add User-agent OS attributes (open-telemetry#1434)

Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>
Co-authored-by: Joao Grassi <5938087+joaopgrassi@users.noreply.github.com>

Author: 3 people

.chloggen/user_agent_os.yaml

@@ -0,0 +1,22 @@
+# Use this changelog template to create an entry for release notes.
+#
+# If your change doesn't affect end users you should instead start
+# your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'enhancement'
+
+# The name of the area of concern in the attributes-registry, (e.g. http, cloud, db)
+component: user-agent
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add `user_agent.os.name` and `user_agent.os.version` attributes
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+# The values here must be integers.
+issues: [1433]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

docs/attributes-registry/user-agent.md

@@ -3,6 +3,9 @@
 
 # User agent
 
+- [User-agent Attributes](#user-agent-attributes)
+- [User-agent OS Attributes](#user-agent-os-attributes)
+
 ## User-agent Attributes
 
 Describes user-agent attributes.
@@ -11,14 +14,27 @@ Describes user-agent attributes.
 |---|---|---|---|---|
 | <a id="user-agent-name" href="#user-agent-name">`user_agent.name`</a> | string | Name of the user-agent extracted from original. Usually refers to the browser's name. [1] | `Safari`; `YourApp` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | <a id="user-agent-original" href="#user-agent-original">`user_agent.original`</a> | string | Value of the [HTTP User-Agent](https://www.rfc-editor.org/rfc/rfc9110.html#field.user-agent) header sent by the client. | `CERN-LineMode/2.15 libwww/2.17b3`; `Mozilla/5.0 (iPhone; CPU iPhone OS 14_7_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.1.2 Mobile/15E148 Safari/604.1`; `YourApp/1.0.0 grpc-java-okhttp/1.27.2` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| <a id="user-agent-synthetic-type" href="#user-agent-synthetic-type">`user_agent.synthetic.type`</a> | string | Specifies the category of synthetic traffic, such as tests or bots. [2] | `bot`; `test` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
-| <a id="user-agent-version" href="#user-agent-version">`user_agent.version`</a> | string | Version of the user-agent extracted from original. Usually refers to the browser's version [3] | `14.1.2`; `1.0.0` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| <a id="user-agent-version" href="#user-agent-version">`user_agent.version`</a> | string | Version of the user-agent extracted from original. Usually refers to the browser's version [2] | `14.1.2`; `1.0.0` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 
 **[1] `user_agent.name`:** [Example](https://www.whatsmyua.info) of extracting browser's name from original string. In the case of using a user-agent for non-browser products, such as microservices with multiple names/versions inside the `user_agent.original`, the most significant name SHOULD be selected. In such a scenario it should align with `user_agent.version`
 
-**[2] `user_agent.synthetic.type`:** This attribute MAY be derived from the contents of the `user_agent.original` attribute. Components that populate the attribute are responsible for determining what they consider to be synthetic bot or test traffic. This attribute can either be set for self-identification purposes, or on telemetry detected to be generated as a result of a synthetic request. This attribute is useful for distinguishing between genuine client traffic and synthetic traffic generated by bots or tests.
+**[2] `user_agent.version`:** [Example](https://www.whatsmyua.info) of extracting browser's version from original string. In the case of using a user-agent for non-browser products, such as microservices with multiple names/versions inside the `user_agent.original`, the most significant version SHOULD be selected. In such a scenario it should align with `user_agent.name`
+
+## User-agent OS Attributes
+
+Describes the OS user-agent attributes.
+
+| Attribute | Type | Description | Examples | Stability |
+|---|---|---|---|---|
+| <a id="user-agent-os-name" href="#user-agent-os-name">`user_agent.os.name`</a> | string | Human readable operating system name. [3] | `iOS`; `Android`; `Ubuntu` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| <a id="user-agent-os-version" href="#user-agent-os-version">`user_agent.os.version`</a> | string | The version string of the operating system as defined in [Version Attributes](/docs/resource/README.md#version-attributes). [4] | `14.2.1`; `18.04.1` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| <a id="user-agent-synthetic-type" href="#user-agent-synthetic-type">`user_agent.synthetic.type`</a> | string | Specifies the category of synthetic traffic, such as tests or bots. [5] | `bot`; `test` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+
+**[3] `user_agent.os.name`:** For mapping user agent strings to OS names, libraries such as [ua-parser](https://github.com/ua-parser) can be utilized.
+
+**[4] `user_agent.os.version`:** For mapping user agent strings to OS versions, libraries such as [ua-parser](https://github.com/ua-parser) can be utilized.
 
-**[3] `user_agent.version`:** [Example](https://www.whatsmyua.info) of extracting browser's version from original string. In the case of using a user-agent for non-browser products, such as microservices with multiple names/versions inside the `user_agent.original`, the most significant version SHOULD be selected. In such a scenario it should align with `user_agent.name`
+**[5] `user_agent.synthetic.type`:** This attribute MAY be derived from the contents of the `user_agent.original` attribute. Components that populate the attribute are responsible for determining what they consider to be synthetic bot or test traffic. This attribute can either be set for self-identification purposes, or on telemetry detected to be generated as a result of a synthetic request. This attribute is useful for distinguishing between genuine client traffic and synthetic traffic generated by bots or tests.
 
 ---
 

model/user-agent/registry.yaml

@@ -35,6 +35,29 @@ groups:
           using a user-agent for non-browser products, such as microservices with multiple names/versions inside the
           `user_agent.original`, the most significant version SHOULD be selected. In such a scenario it should align
           with `user_agent.name`
+
+  - id: registry.user_agent.os
+    type: attribute_group
+    display_name: User-agent OS Attributes
+    brief: "Describes the OS user-agent attributes."
+    attributes:
+      - id: user_agent.os.name
+        type: string
+        stability: experimental
+        brief: 'Human readable operating system name.'
+        examples: ['iOS', 'Android', 'Ubuntu']
+        note: >
+          For mapping user agent strings to OS names, libraries such as [ua-parser](https://github.com/ua-parser) can be utilized.
+      - id: user_agent.os.version
+        type: string
+        stability: experimental
+        brief: >
+          The version string of the operating system as defined in
+          [Version Attributes](/docs/resource/README.md#version-attributes).
+        examples: ['14.2.1', '18.04.1']
+        note: >
+          For mapping user agent strings to OS versions, libraries such as [ua-parser](https://github.com/ua-parser) can be utilized.
+
       - id: user_agent.synthetic.type
         stability: experimental
         brief: >