Make better use of i18n (#20096)

* Prototyping

* Start work on creating offsets

* Modify tests

* Start prototyping with actual MPH

* Twiddle around

* Twiddle around comments

* Convert templates

* Fix external languages

* Fix latest translation

* Fix some test

* Tidy up code

* Use simple map

* go mod tidy

* Move back to data structure

- Uses less memory by creating for each language a map.

* Apply suggestions from code review

Co-authored-by: delvh <dev.lh@web.de>

* Add some comments

* Fix tests

* Try to fix tests

* Use en-US as defacto fallback

* Use correct slices

* refactor (#4)

* Remove TryTr, add log for missing translation key

* Refactor i18n

- Separate dev and production locale stores.
- Allow for live-reloading in dev mode.

Co-authored-by: zeripath <art27@cantab.net>

* Fix live-reloading & check for errors

* Make linter happy

* live-reload with periodic check (#5)

* Fix tests

Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>

integrations/branches_test.go

@@ -9,7 +9,7 @@ import (
 	"net/url"
 	"testing"
 
-	"code.gitea.io/gitea/modules/translation/i18n"
+	"code.gitea.io/gitea/modules/translation"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -37,7 +37,7 @@ func TestUndoDeleteBranch(t *testing.T) {
 		htmlDoc, name := branchAction(t, ".undo-button")
 		assert.Contains(t,
 			htmlDoc.doc.Find(".ui.positive.message").Text(),
-			i18n.Tr("en", "repo.branch.restore_success", name),
+			translation.NewLocale("en-US").Tr("repo.branch.restore_success", name),
 		)
 	})
 }
@@ -46,7 +46,7 @@ func deleteBranch(t *testing.T) {
 	htmlDoc, name := branchAction(t, ".delete-branch-button")
 	assert.Contains(t,
 		htmlDoc.doc.Find(".ui.positive.message").Text(),
-		i18n.Tr("en", "repo.branch.deletion_success", name),
+		translation.NewLocale("en-US").Tr("repo.branch.deletion_success", name),
 	)
 }