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>

modules/setting/repository.go

@@ -58,7 +58,7 @@ var (
 		Upload struct {
 			Enabled      bool
 			TempPath     string
-			AllowedTypes []string `delim:"|"`
+			AllowedTypes string
 			FileMaxSize  int64
 			MaxFiles     int
 		} `ini:"-"`
@@ -85,6 +85,10 @@ var (
 			LockReasons []string
 		} `ini:"repository.issue"`
 
+		Release struct {
+			AllowedTypes string
+		} `ini:"repository.release"`
+
 		Signing struct {
 			SigningKey        string
 			SigningName       string
@@ -165,13 +169,13 @@ var (
 		Upload: struct {
 			Enabled      bool
 			TempPath     string
-			AllowedTypes []string `delim:"|"`
+			AllowedTypes string
 			FileMaxSize  int64
 			MaxFiles     int
 		}{
 			Enabled:      true,
 			TempPath:     "data/tmp/uploads",
-			AllowedTypes: []string{},
+			AllowedTypes: "",
 			FileMaxSize:  3,
 			MaxFiles:     5,
 		},
@@ -213,6 +217,12 @@ var (
 			LockReasons: strings.Split("Too heated,Off-topic,Spam,Resolved", ","),
 		},
 
+		Release: struct {
+			AllowedTypes string
+		}{
+			AllowedTypes: "",
+		},
+
 		// Signing settings
 		Signing: struct {
 			SigningKey        string