API: Extract OpenAPI specification from source code using go-swagger (#40528)

* API: Using go-swagger for extracting OpenAPI specification from source code

* Merge Grafana Alerting spec

* Include enterprise endpoints (if enabled)

* Serve SwaggerUI under feature flag

* Fix building dev docker images

* Configure swaggerUI

* Add missing json tags

Co-authored-by: Ying WANG <ying.wang@grafana.com>
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

pkg/api/docs/definitions/meta.go

@@ -0,0 +1,31 @@
+// Package api Grafana HTTP API.
+//
+// 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.
+//
+// Schemes: http, https
+// BasePath: /api
+// Version: 0.0.1
+// License: GNU Affero General Public License v3.0 https://www.gnu.org/licenses/agpl-3.0.en.html
+// Contact: Grafana Labs<hello@grafana.com> https://grafana.com
+//
+// Consumes:
+// - application/json
+//
+// Produces:
+// - application/json
+//
+// Security:
+// - basic:
+// - api_key:
+//
+// SecurityDefinitions:
+// basic:
+//  type: basic
+// api_key:
+//  type: apiKey
+//  name: Authorization
+//  in: header
+//
+// swagger:meta
+package definitions