Add changelog verifier workflow (#974)

Signed-off-by: Owais <owaiskazi19@gmail.com>

Author: owaiskazi19

.github/workflows/changelog_verifier.yml

@@ -0,0 +1,27 @@
+
+Viewed
+Original file line number 	Diff line number 	Diff line change
+@@ -0,0 +1,23 @@
+name: "Changelog Verifier"
+on:
+  push:
+    branches-ignore:
+      - 'whitesource-remediate/**'
+      - 'backport/**'
+  pull_request:
+    types: [opened, edited, review_requested, synchronize, reopened, ready_for_review, labeled, unlabeled]
+
+jobs:
+  # Enforces the update of a changelog file on every pull request
+  verify-changelog:
+    if: github.repository == 'opensearch-project/anomaly-detection'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - uses: dangoslen/changelog-enforcer@v3
+        with:
+          skipLabels: "autocut, skip-changelog" 

CHANGELOG.md

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+# CHANGELOG
+All notable changes to this project are documented in this file.
+
+Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
+
+## [Unreleased 3.0](https://github.com/opensearch-project/anomaly-detection/compare/2.x...HEAD)
+### Features
+### Enhancements
+### Bug Fixes
+### Infrastructure
+
+### Documentation
+
+### Maintenance
+### Refactoring
+
+## [Unreleased 2.x](https://github.com/opensearch-project/anomaly-detection/compare/2.19...2.x)
+### Features
+
+
+### Enhancements
+- Github workflow for changelog verification ([#974](https://github.com/opensearch-project/anomaly-detection/pull/974))
+### Bug Fixes
+
+### Infrastructure
+### Documentation
+### Maintenance
+### Refactoring

DEVELOPER_GUIDE.md

@@ -9,6 +9,7 @@
     - [Integration Tests](#integration-tests)
   - [Formatting](#formatting)
   - [Backports](#backports)
+  - [Changelog](#changelog)
 
 ## Developer guide
 
@@ -94,3 +95,20 @@ original PR with an appropriate label `backport <backport-branch-name>` is merge
 run successfully on the PR. For example, if a PR on main needs to be backported to `1.x` branch, add a label
 `backport 1.x` to the PR and make sure the backport workflow runs on the PR along with other checks. Once this PR is
 merged to main, the workflow will create a backport PR to the `1.x` branch.
+
+## Changelog
+
+AD dashboards maintains version specific changelog by enforcing a change to the ongoing [CHANGELOG](CHANGELOG.md) file adhering to the [Keep A Changelog](https://keepachangelog.com/en/1.1.0/) format.
+
+Briefly, the changes are curated by version, with the changes to the main branch added chronologically to `Unreleased` version. Further, each version has corresponding sections which list out the category of the change - `Added`, `Changed`, `Deprecated`, `Removed`, `Fixed`, `Security`.
+
+#### How to add my changes to [CHANGELOG](CHANGELOG.md)?
+
+As a contributor, you must ensure that every pull request has the changes listed out within the corresponding version and appropriate section of [CHANGELOG](CHANGELOG.md) file.
+
+Adding in the change is two step process -
+1. Add your changes to the corresponding section within the CHANGELOG file with dummy pull request information, publish the PR
+
+`Your change here ([#PR_NUMBER](PR_URL))`
+
+2. Update the entry for your change in [`CHANGELOG.md`](CHANGELOG.md) and make sure that you reference the pull request there.