[6.x] GraphQL API Authentication

[duncanmcclean]

This pull request adds authentication to the GraphQL API.

To enable, add the STATAMIC_GRAPHQL_AUTH_TOKEN key to your .env:

STATAMIC_GRAPHQL_AUTH_TOKEN=some-random-string

Then, when making requests to the GraphQL API, include the API token as a header:

curl -X GET "https://example.com/graphql" \
  -H "Authorization: Bearer some-random-string" \
  -H "Accept: application/json"
  -d '{"query": "{ping}"}'

If you need full-on user authentication, we recommend using something like Laravel Sanctum instead.

We added authentication to the REST API in #12051, and ever since then I've been meaning to add it to GraphQL too for feature parity, so here we are!