[MM-15639] Add config setting to explicitly define which IP headers are trusted (#10907)

* Add config setting to explicitly define which IP headers are trusted

* fix variable shadowing

* Optimize code flow; Add Ratelimit test for header set

* Extend Ratelimit tests

* Add additional unit tests

* Structured logging

app/plugin_requests.go

@@ -74,7 +74,7 @@ func (a *App) servePluginRequest(w http.ResponseWriter, r *http.Request, handler
 	token := ""
 	context := &plugin.Context{
 		RequestId:      model.NewId(),
-		IpAddress:      utils.GetIpAddress(r),
+		IpAddress:      utils.GetIpAddress(r, a.Config().ServiceSettings.TrustedProxyIPHeader),
 		AcceptLanguage: r.Header.Get("Accept-Language"),
 		UserAgent:      r.UserAgent(),
 	}