Correlations: Add CreateCorrelation HTTP API (#51630)

* Correlations: add migration

* Correlations: Add CreateCorrelation API

* Correlations: Make correlations work with provisioning

* Handle version changes

* Fix lining error

* lint fixes

* rebuild betterer results

* add a UID to each correlation

* Fix lint errors

* add docs

* better wording in API docs

* remove leftover comment

* handle ds updates

* Fix error message typo

* add bad data test

* make correlations a separate table

* skip readonly check when provisioning correlations

* delete stale correlations when datasources are deleted

* restore provisioned readonly ds

* publish deletion event with full data

* generate swagger and HTTP API docs

* apply source datasource permission to create correlation API

* Fix tests & lint errors

* ignore empty deletion events

* fix last lint errors

* fix more lint error

* Only publish deletion event if datasource was actually deleted

* delete DS provisioning deletes correlations, added & fixed tests

* Fix unmarshalling tests

* Fix linting errors

* Fix deltion event tests

* fix small linting error

* fix lint errors

* update betterer

* fix test

* make path singular

* Revert "make path singular"

This reverts commit 420c3d315e.

* add integration tests

* remove unneeded id from correlations table

* update spec

* update leftover references to CorrelationDTO

* fix tests

* cleanup tests

* fix lint error

docs/sources/developers/http_api/correlations.md

@@ -0,0 +1,70 @@
+---
+aliases:
+  - /docs/grafana/latest/developers/http_api/correlations/
+  - /docs/grafana/latest/http_api/correlations/
+description: Grafana Correlations HTTP API
+keywords:
+  - grafana
+  - http
+  - documentation
+  - api
+  - correlations
+  - Glue
+title: 'Correlations HTTP API '
+---
+
+# Correlations API
+
+This API can be used to define correlations between data sources.
+
+## Create correlations
+
+`POST /api/datasources/uid/:sourceUid/correlations`
+
+Creates a correlation between two data sources - the source data source indicated by the path UID, and the target data source which is specified in the body.
+
+**Example request:**
+
+```http
+POST /api/datasources/uid/uyBf2637k/correlations HTTP/1.1
+Accept: application/json
+Content-Type: application/json
+Authorization: Bearer eyJrIjoiT0tTcG1pUlY2RnVKZTFVaDFsNFZXdE9ZWmNrMkZYbk
+{
+```
+
+JSON body schema:
+
+- **targetUid** – Target data source uid.
+- **label** – A label for the correlation.
+- **description** – A description for the correlation.
+
+**Example response:**
+
+```http
+HTTP/1.1 200
+Content-Type: application/json
+{
+```
+
+Status codes:
+
+- **200** – OK
+- **400** - Errors (invalid JSON, missing or invalid fields)
+- **401** – Unauthorized
+- **403** – Forbidden, source data source is read-only
+- **404** – Not found, either source or target data source could not be found
+- **500** – Internal error
+    "uid": "50xhMlg9k"
+  }
+}
+```
+
+Status codes:
+
+- **200** – OK
+- **400** - Errors (invalid JSON, missing or invalid fields)
+- **401** – Unauthorized
+- **403** – Forbidden, source data source is read-only
+- **404** – Not found, either source or target data source could not be found
+- **500** – Internal error