MM-45536: Track GraphQL queries in Grafana (#20609)

https://mattermost.atlassian.net/browse/MM-45536

```release-note
NONE
```

api4/graphql.go

@@ -101,6 +101,8 @@ func (api *API) graphQL(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	c.GraphQLOperationName = params.OperationName
+
 	// Populate the context with required info.
 	reqCtx := r.Context()
 	reqCtx = context.WithValue(reqCtx, webCtx, c)

web/context.go

@@ -19,12 +19,15 @@ import (
 )
 
 type Context struct {
-	App           app.AppIface
-	AppContext    *request.Context
-	Logger        *mlog.Logger
-	Params        *Params
-	Err           *model.AppError
-	siteURLHeader string
+	App        app.AppIface
+	AppContext *request.Context
+	Logger     *mlog.Logger
+	Params     *Params
+	Err        *model.AppError
+	// This is used to track the graphQL query that's being executed,
+	// so that we can monitor the timings in Grafana.
+	GraphQLOperationName string
+	siteURLHeader        string
 }
 
 // LogAuditRec logs an audit record using default LevelAPI.

web/handlers.go

@@ -382,7 +382,14 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 		if r.URL.Path != model.APIURLSuffix+"/websocket" {
 			elapsed := float64(time.Since(now)) / float64(time.Second)
-			c.App.Metrics().ObserveAPIEndpointDuration(h.HandlerName, r.Method, statusCode, elapsed)
+			var endpoint string
+			if strings.HasPrefix(r.URL.Path, model.APIURLSuffixV5) {
+				// It's a graphQL query, so use the operation name.
+				endpoint = c.GraphQLOperationName
+			} else {
+				endpoint = h.HandlerName
+			}
+			c.App.Metrics().ObserveAPIEndpointDuration(endpoint, r.Method, statusCode, elapsed)
 		}
 	}
 }