[chore] Rationalize HTTP return codes for fedi endpoints, other tidying up (#4503)

# Description

> If this is a code change, please include a summary of what you've coded, and link to the issue(s) it closes/implements.
>
> If this is a documentation change, please briefly describe what you've changed and why.

This pull request does some refactoring of the fedi API endpoints and processing functions, and the authenticate + pub key deref functions, to try to return fewer silly HTTP codes like 410 Gone (when a *remote* account is gone, not a local one), and 500 errors where something isn't really an error.

Also does some general tidying up and renaming for consistency.

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [ ] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4503
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/internal/api/activitypub/users/inboxpost_test.go b/internal/api/activitypub/users/inboxpost_test.go
index 51df35672..facf2b459 100644
--- a/internal/api/activitypub/users/inboxpost_test.go
+++ b/internal/api/activitypub/users/inboxpost_test.go
@@ -31,7 +31,7 @@ import (
 	"code.superseriousbusiness.org/activity/streams"
 	"code.superseriousbusiness.org/activity/streams/vocab"
 	"code.superseriousbusiness.org/gotosocial/internal/ap"
-	"code.superseriousbusiness.org/gotosocial/internal/api/activitypub/users"
+	apiutil "code.superseriousbusiness.org/gotosocial/internal/api/util"
 	"code.superseriousbusiness.org/gotosocial/internal/db"
 	"code.superseriousbusiness.org/gotosocial/internal/gtserror"
 	"code.superseriousbusiness.org/gotosocial/internal/gtsmodel"
@@ -79,7 +79,7 @@ func (suite *InboxPostTestSuite) inboxPost(
 	)
 
 	// Put the request together.
-	ctx.AddParam(users.UsernameKey, targetAccount.Username)
+	ctx.AddParam(apiutil.UsernameKey, targetAccount.Username)
 	ctx.Request = httptest.NewRequest(http.MethodPost, targetAccount.InboxURI, bytes.NewReader(b))
 	ctx.Request.Header.Set("Signature", signature)
 	ctx.Request.Header.Set("Date", dateHeader)