Fix various permission & login related bugs (#36002)

Permission & protection check:

- Fix Delete Release permission check
- Fix Update Pull Request with rebase branch protection check
- Fix Issue Dependency permission check
- Fix Delete Comment History ID check

Information leaking:

- Show unified message for non-existing user and invalid password
    - Fix #35984
- Don't expose release draft to non-writer users.
- Make API returns signature's email address instead of the user
profile's.

Auth & Login:

- Avoid GCM OAuth2 attempt when OAuth2 is disabled
    - Fix #35510

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/githttp.go

@@ -146,7 +146,13 @@ func httpBase(ctx *context.Context) *serviceHandler {
 		// rely on the results of Contexter
 		if !ctx.IsSigned {
 			// TODO: support digit auth - which would be Authorization header with digit
-			ctx.Resp.Header().Set("WWW-Authenticate", `Basic realm="Gitea"`)
+			if setting.OAuth2.Enabled {
+				// `Basic realm="Gitea"` tells the GCM to use builtin OAuth2 application: https://github.com/git-ecosystem/git-credential-manager/pull/1442
+				ctx.Resp.Header().Set("WWW-Authenticate", `Basic realm="Gitea"`)
+			} else {
+				// If OAuth2 is disabled, then use another realm to avoid GCM OAuth2 attempt
+				ctx.Resp.Header().Set("WWW-Authenticate", `Basic realm="Gitea (Basic Auth)"`)
+			}
 			ctx.HTTPError(http.StatusUnauthorized)
 			return nil
 		}