start working on oauth2 implementation

internal/db/db.go

@@ -24,6 +24,7 @@ import (
 	"strings"
 
 	"github.com/go-fed/activity/pub"
+	"github.com/go-oauth2/oauth2/v4"
 	"github.com/gotosocial/gotosocial/internal/config"
 	"github.com/sirupsen/logrus"
 )
@@ -39,6 +40,11 @@ type DB interface {
 	*/
 	pub.Database
 
+	/*
+		OAUTH2 DATABASE FUNCTIONS
+	*/
+	TokenStore() oauth2.TokenStore
+
 	/*
 		ANY ADDITIONAL DESIRED FUNCTIONS
 	*/