Handle case of short manually set single-user API keys

Co-authored-by: Padraic Shafer <76011594+padraic-shafer@users.noreply.github.com>

tiled/client/context.py

@@ -172,7 +172,7 @@ def __repr__(self):
                     ",".join(f"'{identity['id']}'" for identity in identities)
                 )
             if self.api_key is not None:
-                auth_info.append(f"with API key '{self.api_key[:8]}...'")
+                auth_info.append(f"with API key '{self.api_key[:min(len(self.api_key)//2, 8)]}...'")
         auth_repr = " ".join(auth_info)
         return f"<{type(self).__name__} {auth_repr}>"