feat: correct password app reset token call and handle missing users

Fixes for https://gitlab.developers.cam.ac.uk/uis/devops/iam/activate-account/api/-/issues/25

Now returns a 400 - validation error

{
    "crsid": "Password App was unable to find the user"
}

Or 503 - service unavailable - on any other failure

And doesn't retry if the password app couldn't find the user (aka raven db said it didn't exist to set the token on)

activate_account/reset_tokens.py

@@ -43,7+43,7 @@
     reporting the failure back to frontend.
     """
 
     try:
         request = requests.get(
             settings.PASSWORD_APP_RESET_TOKEN_URL,
             headers={"Authorization": f"Token {settings.PASSWORD_APP_TOKEN}"},
@@ -52,7+52,7 @@
         )
         request.raise_for_status()
         return PasswordAppTokenResponse(**request.json())
-    except Exception as e:
-        logger.error("get_reset_token", error="Failed to get reset token", exc=repr(e))
-        if isinstance(e, requests.HTTPError) and e.response.status_code == 404:
+    except requests.HTTPError as e:
+        if e.response.status_code == 404:
+            logger.error(
+                "get_reset_token_not_found",
+                error="Password reset token retrieval failed: User not found",
+                exc=repr(e),
+            )
             raise PasswordAppNotFound
+        logger.error(
+            "get_reset_token_http_error",
+            error="Password reset token retrieval failed: HTTP error",
+            exc=repr(e),
+        )
+        raise e
+    except requests.RequestException as e:
+        logger.error(
+            "get_reset_token",
+            error="Password reset token retrieval failed: Network issue",
+            exc=repr(e),
+        )
         raise e