NRL-518 Fix pydantic error reporting

Author: axelkrastek1-nhs

layer/nrlf/core/errors.py

@@ -11,14 +11,14 @@
 
 def diag_for_error(error: ErrorDetails) -> str:
     if error["loc"]:
-        loc_string = ".".join(each for each in error["loc"])
+        loc_string = ".".join(str(each) for each in error["loc"])
         return f"{loc_string}: {error['msg']}"
     else:
         return f"root: {error['msg']}"
 
 
 def expression_for_error(error: ErrorDetails) -> Optional[str]:
-    return str(".".join(each for each in error["loc"]) if error["loc"] else "root")
+    return str(".".join(str(each) for each in error["loc"]) if error["loc"] else "root")
 
 
 class OperationOutcomeError(Exception):