client/graphql: handle GraphQL errors
Instead of leaving it up to the caller to check for GraphQL errors,
centralize in core-go.
client: add config option to override API origin
If the config file contains an "api-origin" key for a service, prefer it
instead of "origin". This allows users to directly point the Python
frontend to the Go backend for local development, without having to
setup a reverse proxy.
This is the Go port of [1].
While at it, use GetOrigin for symmetry with the Python code.
[1]: https://git.sr.ht/~sircmpwn/meta.sr.ht/commit/6c2ee03923fe65423a2c55e6648f555c08db827a
client: populate NodeID from service name
Drop leftover references to gql.sr.ht
client: import from gql.sr.ht