feat(nhost_flutter_auth): Allow displayName and locale to be passed on signInAnonymous

[sl1mpshady]

Added this PR with regards to https://github.com/nhost/hasura-auth/blob/main/src/routes/signin/anonymous.ts that allows user to send displayName and locale to override the default "Anonymous User". Also, session should be set after signing in.

[sl1mpshady]

How to make the checks pass?

Run PERCENTAGE=$((( $TOTAL ) * 100 / ( $TOTAL_MAX - ${MAX_PANA_MISSING_POINTS:-10} )))
  PERCENTAGE=$((( $TOTAL ) * 100 / ( $TOTAL_MAX - ${MAX_PANA_MISSING_POINTS:-10} )))
  if (( $PERCENTAGE < 100 ))
  then
    echo "Score to low ($TOTAL/$TOTAL_MAX)."
    exit 1
  fi
  shell: /usr/bin/bash -e {0}
  env:
    TOTAL: 1[2](https://github.com/nhost/nhost-dart/actions/runs/7671882054/job/21057417995?pr=131#step:6:2)0
    TOTAL_MAX: 1[4](https://github.com/nhost/nhost-dart/actions/runs/7671882054/job/21057417995?pr=131#step:6:4)0
Score to low ([12](https://github.com/nhost/nhost-dart/actions/runs/7671882054/job/21057417995?pr=131#step:6:13)0/140).
Error: Process completed with exit code 1.

[dbarrosop]

would you mind adding metadata too now that we are at it? Should just be an arbitrary map.

[sl1mpshady]

metadata is ignored at the moment on nhost hasura_auth, so metadata will not be saved on user's side. but i added it just in case in the future hasura_auth will allow sending the metada for signing in anonymously.

@dbarrosop

[sl1mpshady]

Added metadata and also modified the function to set the session after api call. @dbarrosop