Correctly escape variables when templating GraphiQL response

[yrd]

This commit makes sure that values are escaped correctly when doing re.sub() while rendering a GraphiQL response. This is necessary when non-ASCII characters end up in the GraphQL variables, for example an umlaut. json.dumps()encodes such characters using a unicode escape sequence starting with \u, which isn't a valid regex. Hence, we would get this error:

re.error: bad escape \u at position 11

Traceback

../.venv/lib/python3.9/site-packages/werkzeug/test.py:1006: in get
    return self.open(*args, **kw)
../.venv/lib/python3.9/site-packages/flask/testing.py:222: in open
    return Client.open(
../.venv/lib/python3.9/site-packages/werkzeug/test.py:970: in open
    response = self.run_wsgi_app(environ.copy(), buffered=buffered)
../.venv/lib/python3.9/site-packages/werkzeug/test.py:861: in run_wsgi_app
    rv = run_wsgi_app(self.application, environ, buffered=buffered)
../.venv/lib/python3.9/site-packages/werkzeug/test.py:1096: in run_wsgi_app
    app_rv = app(environ, start_response)
../.venv/lib/python3.9/site-packages/flask/app.py:2464: in __call__
    return self.wsgi_app(environ, start_response)
../.venv/lib/python3.9/site-packages/flask/app.py:2450: in wsgi_app
    response = self.handle_exception(e)
../.venv/lib/python3.9/site-packages/flask/app.py:1867: in handle_exception
    reraise(exc_type, exc_value, tb)
../.venv/lib/python3.9/site-packages/flask/_compat.py:39: in reraise
    raise value
../.venv/lib/python3.9/site-packages/flask/app.py:2447: in wsgi_app
    response = self.full_dispatch_request()
../.venv/lib/python3.9/site-packages/flask/app.py:1952: in full_dispatch_request
    rv = self.handle_user_exception(e)
../.venv/lib/python3.9/site-packages/flask/app.py:1821: in handle_user_exception
    reraise(exc_type, exc_value, tb)
../.venv/lib/python3.9/site-packages/flask/_compat.py:39: in reraise
    raise value
../.venv/lib/python3.9/site-packages/flask/app.py:1950: in full_dispatch_request
    rv = self.dispatch_request()
../.venv/lib/python3.9/site-packages/flask/app.py:1936: in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
../.venv/lib/python3.9/site-packages/flask/views.py:89: in view
    return self.dispatch_request(*args, **kwargs)
../graphql_server/flask/graphqlview.py:136: in dispatch_request
    source = render_graphiql_sync(
../graphql_server/render_graphiql.py:329: in render_graphiql_sync
    source = simple_renderer(graphiql_template, **template_vars)
../graphql_server/render_graphiql.py:262: in simple_renderer
    template = process_var(template, r, values.get(r, ""), True)
../graphql_server/render_graphiql.py:238: in process_var
    return re.sub(pattern, value, template)
/nix/store/x26srysgpc16zvxz5fdk0kdqd92i4h5i-python3-3.9.13/lib/python3.9/re.py:210: in sub
    return _compile(pattern, flags).sub(repl, string, count)
/nix/store/x26srysgpc16zvxz5fdk0kdqd92i4h5i-python3-3.9.13/lib/python3.9/re.py:327: in _subx
    template = _compile_repl(template, pattern)
/nix/store/x26srysgpc16zvxz5fdk0kdqd92i4h5i-python3-3.9.13/lib/python3.9/re.py:318: in _compile_repl
    return sre_parse.parse_template(repl, pattern)

We get around this by re.escape()-ing everything before doing anything regexy with it.