MM-21898 - Part 1: Generate and use an interface instead of *A… (#13840)

* Generate and use an interface instead of *App

app/plugin_context.go

@@ -7,11 +7,11 @@ import "github.com/mattermost/mattermost-server/v5/plugin"
 
 func (a *App) PluginContext() *plugin.Context {
 	context := &plugin.Context{
-		RequestId:      a.RequestId,
-		SessionId:      a.Session.Id,
-		IpAddress:      a.IpAddress,
-		AcceptLanguage: a.AcceptLanguage,
-		UserAgent:      a.UserAgent,
+		RequestId:      a.RequestId(),
+		SessionId:      a.Session().Id,
+		IpAddress:      a.IpAddress(),
+		AcceptLanguage: a.AcceptLanguage(),
+		UserAgent:      a.UserAgent(),
 	}
 	return context
 }