Attachments: Add extension support, allow all types for releases (#12465)

* Attachments: Add extension support, allow all types for releases

- Add support for file extensions, matching the `accept` attribute of `<input type="file">`
- Add support for type wildcard mime types, e.g. `image/*`
- Create repository.release.ALLOWED_TYPES setting (default unrestricted)
- Change default for attachment.ALLOWED_TYPES to a list of extensions
- Split out POST /attachments into two endpoints for issue/pr and
  releases to prevent circumvention of allowed types check

Fixes: https://github.com/go-gitea/gitea/pull/10172
Fixes: https://github.com/go-gitea/gitea/issues/7266
Fixes: https://github.com/go-gitea/gitea/pull/12460
Ref: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/file#Unique_file_type_specifiers

* rename function

* extract GET routes out of RepoMustNotBeArchived

Co-authored-by: Lauris BH <lauris@nix.lv>

routers/repo/compare.go

@@ -17,6 +17,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/upload"
 	"code.gitea.io/gitea/services/gitdiff"
 )
 
@@ -578,7 +579,8 @@ func CompareDiff(ctx *context.Context) {
 	ctx.Data["RequireSimpleMDE"] = true
 	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
 	setTemplateIfExists(ctx, pullRequestTemplateKey, nil, pullRequestTemplateCandidates)
-	renderAttachmentSettings(ctx)
+	ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
+	upload.AddUploadContext(ctx, "comment")
 
 	ctx.Data["HasIssuesOrPullsWritePermission"] = ctx.Repo.CanWrite(models.UnitTypePullRequests)