auth: remove legacy OAuth support

auth: fix remote IP determination for audit log

This is probably isolated to dev or other small environments, but I had
two issues with the remote IP determination, breaking the audit log
display in my dev env after fairly standard usage.

The gist is that the audit log is designed to contain clean IP addresses
only. However, the algorithm starts out with `r.RemoteAddr`, which may
contain a port (usually 127.0.0.1:xxxxx). The port removal is already
performed at the beginning of the function, so simply re-use the result
of this.

Furthermore, the initial value (containing the port leading to breakage)
landed in the audit log because I was using a private IP (it's my dev
evn). We correctly trust private IPs, but that means if no public IP
ever shows up in the X-Forwarded-For header, the last private IP was the
one that actually made the request.

I am not entirely sure why this showed up now. I already had a bunch of
oder audit log entries that had the correct private-but-not-localhost
addresses. But in the current state, e.g. simply updating my profile
would cause the bad IP:port notation to be written to the audit log.

webhooks: implement internal webhook users

AUTH_INTERNAL requests previously could not register webhooks. This
commit adds the necessary changes to allow for this.

auth: use config.IsInternalIP

auth: reduce scope of user_type

auth: grant scoped access to anon internal auth

Internal auth is granted access to everything, whereas anonymous
internal auth is pretty restricted. This is mostly to avoid accidentally
hitting resolvers that require a logged-in user, however. Given that all
anon internal use cases are hard-coded and tested, this seems like a
pretty low risk. Allowing this will have the huge benefit of making much
more information available to anon internal queries, which will unlock
removing a bunch of awkward work-arounds we put in place.

Note, however, that this is also a work-around. It saves us from adding
yet more work-arounds to the GQL schema, and in the meantime a redesign
of the schema (especially the directives) is being worked on.

auth/middleware: fix user_type on new users

auth/middleware: convert user types to uppercase

server: use routing groups

Instead of hardcoding some exceptions in the auth middleware, use a
different routing group for routes that do not require auth. Makes the
auth middleware more generic and also removes a lot of unneccessary
middleware processing from routes that don't need it.

For now, the added group is not accessible from outside the module, but
if the need arises, this might be an option.

auth: add auth.IPAddress

With support for X-Forwarded-For

auth/middleware: set WWW-Authenticate header field

See RFC 6750 section 3.

client: rename Execute to Do

583d0b1bcb08 ("client/graphql: handle GraphQL errors") changed
Execute behavior by wrapping the result into a struct with "data"
and "errors" fields. This is a breaking change, but it's hard to
spot when upgrading core-go because it won't cause a compilation
error.

Rename Execute to Do to break the build and force callers to update
accordingly.

auth: add RequireMiddleware

Same as Middleware, but requires auth for all requests. Will be
useful to drop hacks from pages.sr.ht.

Drop gqlparser v1 dependency

Only use v2 throughout the repository.

auth: make DecodeGrants return an error

We'll use this function to validate grants passed in via
builds.sr.ht manifests.

auth: add AuthContext.Access

Same logic as server.Access, but lower-level. Useful to check for
a permission not covered by the GraphQL schema @access directives
(such as builds.sr.ht secrets).

auth: add /query/external/* to anonymous whitelist

auth/middleware: make auth scheme case-insensitive

According to RFC 7235 section 2.1, the auth scheme is
case-insensitive.

auth: fix invalid json tag in InternalAuth

auth: Use canonical user IDs

When adding users to the database, use the canonical user ID from
meta.sr.ht.