docs(http): moves overview content to /http_api/

ref #6719

docs/sources/http_api/index.md

 +++
 title = "HTTP API"
+description = "Grafana HTTP API"
+keywords = ["grafana", "http", "documentation", "api", "overview"]
+type = "docs"
 [menu.docs]
 name = "HTTP API"
 identifier = "http_api"
 weight = 9
 +++
+
+
+# HTTP API Reference
+
+The Grafana backend exposes an HTTP API, the same API is used by the frontend to do everything from saving
+dashboards, creating users and updating data sources.
+
+## Supported HTTP APIs:
+
+* [Authentication API](/http_api/auth/)
+* [Dashboard API](/http_api/dashboard/)
+* [Data Source API](/http_api/data_source/)
+* [Organisation API](/http_api/org/)
+* [User API](/http_api/user/)
+* [Admin API](/http_api/admin/)
+* [Snapshot API](/http_api/snapshot/)
+* [Preferences API](/http_api/preferences/)
+* [Other API](/http_api/other/)

docs/sources/http_api/overview.md

-+++
-title = "HTTP API "
-description = "Grafana HTTP API"
-keywords = ["grafana", "http", "documentation", "api", "overview"]
-aliases = ["/http_api/overview/"]
-type = "docs"
-[menu.docs]
-name = "Overview"
-parent = "http_api"
-+++
-
-
-# HTTP API Reference
-
-The Grafana backend exposes an HTTP API, the same API is used by the frontend to do everything from saving
-dashboards, creating users and updating data sources.
-
-## Supported HTTP APIs:
-
-* [Authentication API](/http_api/auth/)
-* [Dashboard API](/http_api/dashboard/)
-* [Data Source API](/http_api/data_source/)
-* [Organisation API](/http_api/org/)
-* [User API](/http_api/user/)
-* [Admin API](/http_api/admin/)
-* [Snapshot API](/http_api/snapshot/)
-* [Preferences API](/http_api/preferences/)
-* [Other API](/http_api/other/)