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/swagger.go

@@ -0,0 +1,7 @@
+package api
+
+import "github.com/grafana/grafana/pkg/models"
+
+func swaggerUI(c *models.ReqContext) {
+	c.HTML(200, "swagger", nil)
+}