[MM-55268] Implement ServeMetrics plugins hook (#24249)

* Implement ServeMetrics plugins hook

* Update error id

* Simplify

* Revert "Simplify"

This reverts commit c9dc5d5eac6c933ff69e158cf3e34d0973bd3bcd.

* Add comment and error handler

* Wrap error

* Update translation file

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/plugin/plugintest/hooks.go

@@ -360,6 +360,11 @@ func (_m *Hooks) ServeHTTP(c *plugin.Context, w http.ResponseWriter, r *http.Req
 	_m.Called(c, w, r)
 }
 
+// ServeMetrics provides a mock function with given fields: c, w, r
+func (_m *Hooks) ServeMetrics(c *plugin.Context, w http.ResponseWriter, r *http.Request) {
+	_m.Called(c, w, r)
+}
+
 // UserHasBeenCreated provides a mock function with given fields: c, user
 func (_m *Hooks) UserHasBeenCreated(c *plugin.Context, user *model.User) {
 	_m.Called(c, user)