feat: add SNMP models (#17)

Author: kpetremann

docs/docs/CMDB/models/SNMP.md

@@ -0,0 +1,35 @@
+# SNMP
+
+## Source code
+
+Models location: [netbox_cmdb/models/snmp.py](https://github.com/criteo/netbox-network-cmdb/blob/main/netbox_cmdb/netbox_cmdb/models/snmp.py)
+
+## Table relations
+
+!!! info
+
+    To simplify the diagram, not all relations are displayed (example: `DeviceBGPSession` => `IPAM.IPAddress`)
+
+``` mermaid
+erDiagram
+
+    dcim_Device 1--1+ SNMP: ""
+    SNMP 1+--1+ SNMPCommunity: ""
+```
+
+## BGP global configuration
+
+```yaml
+SNMP:
+    device: dcim.Device
+    contact: string
+    location: string
+    community_list: cmdb.SNMPCommunity
+```
+
+```yaml
+SNMPCommunity:
+    SNMPCommunity: string
+    SNMPCommunity: string
+    type: RO|RW
+```