Add source field to debug information for better resolution informa…

…tion

authzed/api/v1/debug.proto

@@ -83,6 +83,11 @@ message CheckDebugTrace {
     // sub_problems holds the sub problems that were executed to resolve the answer to this Check. An empty list
     // and a permissionship of PERMISSIONSHIP_HAS_PERMISSION indicates the subject was found within this relation.
     SubProblems sub_problems = 7;
+
+    // source holds the source of the result. It is of the form:
+    // `<sourcetype>:<sourceid>`, where sourcetype can be, among others:
+    // `spicedb`, `materialize`, etc.
+    string source = 12;
   }
 
   // optional_expires_at is the time at which at least one of the relationships used to