DOC-4970 RS: Added migration status REST API reference

Author: rrelledge

content/operate/rs/references/rest-api/requests/migrations/_index.md

@@ -0,0 +1,75 @@
+---
+Title: Migrations requests
+alwaysopen: false
+categories:
+- docs
+- operate
+- rs
+description: REST API request to get the migration status of a database in the cluster.
+headerRange: '[1-2]'
+hideListLinks: true
+linkTitle: migrations
+weight: $weight
+---
+
+| Method | Path | Description |
+|--------|------|-------------|
+| [GET](#get-migrations) | `/v1/migrations/<uid>` | Get database migration status |
+
+## Get migration status {#get-migrations}
+
+```sh
+GET /v1/migrations/<uid>
+```
+
+Gets the migration status of a database in the cluster.
+
+#### Required permissions
+
+| Permission name |
+|-----------------|
+| [view_bdb_info]({{< relref "/operate/rs/references/rest-api/permissions#view_bdb_info" >}}) |
+
+### Request {#get-request}
+
+#### Example HTTP request
+
+```sh
+GET /v1/migrations/1
+```
+
+#### Headers
+
+| Key | Value | Description |
+|-----|-------|-------------|
+| Host | cnm.cluster.fqdn | Domain name |
+| Accept | application/json | Accepted media type |
+
+#### URL parameters
+
+| Field | Type | Description |
+|-------|------|-------------|
+| uid | integer | The database's unique ID |
+
+### Response {#get-response}
+
+Returns a JSON array with all data required by the Azure migration orchestrator.
+
+#### Example response body
+
+```json
+"migration": {
+    "status": "foo",
+    "lag": 123,
+    "run_id": "5",
+    "flush_counter": 2,
+    "source_shards": [{"replication_id": "1", "replication_offset": 2}]
+}
+```
+
+#### Status codes {#get-status-codes}
+
+| Code | Description |
+|------|-------------|
+| [200 OK](https://www.rfc-editor.org/rfc/rfc9110.html#name-200-ok) | No error |
+| [404 Not Found](https://www.rfc-editor.org/rfc/rfc9110.html#name-404-not-found) | Database does not exist |