For the "This user does not have X" pages.

Signed-off-by: Anirudh Oppiliappan <anirudh@tangled.org>

currently all backlinks are parsed with markdown parser.
So only explict urls like below are supported:

- <https://tangled.org/owner.com/repo-name/issues/123>
- [full url](https://tangled.org/owner.com/repo-name/issues/123)
- [absolute path](/owner.com/repo-name/issues/123)

Also `#comment-123` fragment is supported too.

All references in issue/pull/comment records are stored in at-uri
format. we do have a `mentions` field, but it isn't used yet. mentions
are parsed on rendering and aren't stored anywhere for now.

Signed-off-by: Seongmin Lee <git@boltless.me>

Signed-off-by: Seongmin Lee <git@boltless.me>

Storing references parsed from the markdown body in atproto record and
DB. There can be lots of reference types considering the from/to types
so storing both as AT-URIs

Using `sql.Tx` more to combine multiple DB query to single recoverable
operation.

Note: Pulls don't have mentinos/references yet

Signed-off-by: Seongmin Lee <git@boltless.me>

Defined `refResolver` which will parse useful data from markdown body
like @-mentions or issue/pr/comment mentions

Signed-off-by: Seongmin Lee <git@boltless.me>

Signed-off-by: oppiliappan <me@oppi.li>

Signed-off-by: Seongmin Lee <git@boltless.me>

Signed-off-by: Thomas Karpiniec <tkarpiniec@icloud.com>

Signed-off-by: oppiliappan <me@oppi.li>

detect the host to clone from and use a local clone if possible.

Signed-off-by: oppiliappan <me@oppi.li>

Signed-off-by: Seongmin Lee <git@boltless.me>

Now `ResolvedRepo` is basically same to `models.Repo` so we can safely
remove it. (not included in this commit to make change reviewable size.)

Signed-off-by: Seongmin Lee <git@boltless.me>

Signed-off-by: Seongmin Lee <git@boltless.me>

- remove unused parameters
- pass correct parameters
- rename with `*Fragment` suffix

Signed-off-by: Seongmin Lee <git@boltless.me>

`RepoInfo` is mostly designed for rendering, don't use it for service
logic.

Signed-off-by: Seongmin Lee <git@boltless.me>

replace with rbac enforcer instead

Signed-off-by: Seongmin Lee <git@boltless.me>

Ideally we should completely remove it.

Signed-off-by: Seongmin Lee <git@boltless.me>