feat: added session guid and token type fields to jwt tokens;

feat: very minimal implementation of registration functions;
refactor: login function now uses the transactional db helper function and creates a session;
feat: enum for jwt token type

backend/internal/utils/enums/enums.go

@@ -29,3 +29,9 @@ const (
 	UserRole
 	AdminRole 
 )
+
+type JwtTokenType int32
+const (
+	JwtAccessTokenType JwtTokenType = iota
+	JwtRefreshTokenType
+)