Add option to set language in admin user view (#28449)

![image](https://github.com/go-gitea/gitea/assets/24977596/be7e3f92-af3f-4628-b4ed-abf6439687f3)
`/admin/users/<UserID>/edit`

![image](https://github.com/go-gitea/gitea/assets/24977596/906af0dd-cceb-4ed9-9cd9-32c71ae1bf71)
`/admin/users/<UserID>`

---
*Sponsored by Kithara Software GmbH*

(cherry picked from commit e3e6569c5fd8c69aa65384e6d1636cc14b23a32b)

routers/web/admin/users.go

@@ -439,6 +439,7 @@ func EditUserPost(ctx *context.Context) {
 		AllowCreateOrganization: optional.Some(form.AllowCreateOrganization),
 		IsRestricted:            optional.Some(form.Restricted),
 		Visibility:              optional.Some(form.Visibility),
+		Language:                optional.Some(form.Language),
 	}
 
 	if err := user_service.UpdateUser(ctx, u, opts); err != nil {

services/forms/admin.go

@@ -41,6 +41,7 @@ type AdminEditUserForm struct {
 	Password                string `binding:"MaxSize(255)"`
 	Website                 string `binding:"ValidUrl;MaxSize(255)"`
 	Location                string `binding:"MaxSize(50)"`
+	Language                string `binding:"MaxSize(5)"`
 	MaxRepoCreation         int
 	Active                  bool
 	Admin                   bool

templates/admin/user/edit.tmpl

@@ -70,6 +70,21 @@
 					<input id="password" name="password" type="password" autocomplete="new-password">
 					<p class="help">{{ctx.Locale.Tr "admin.users.password_helper"}}</p>
 				</div>
+
+				<div class="field {{if .Err_Language}}error{{end}}">
+					<label for="language">{{ctx.Locale.Tr "settings.language"}}</label>
+					<div class="ui selection dropdown">
+						<input name="language" type="hidden" value="{{.User.Language}}">
+						{{svg "octicon-triangle-down" 14 "dropdown icon"}}
+						<div class="text">{{range .AllLangs}}{{if eq $.User.Language .Lang}}{{.Name}}{{end}}{{end}}</div>
+						<div class="menu">
+						{{range .AllLangs}}
+							<div class="item{{if eq $.User.Language .Lang}} active selected{{end}}" data-value="{{.Lang}}">{{.Name}}</div>
+						{{end}}
+						</div>
+					</div>
+				</div>
+
 				<div class="field {{if .Err_Website}}error{{end}}">
 					<label for="website">{{ctx.Locale.Tr "settings.website"}}</label>
 					<input id="website" name="website" type="url" value="{{.User.Website}}" placeholder="http://mydomain.com or https://mydomain.com" maxlength="255">

templates/admin/user/view_details.tmpl

@@ -48,6 +48,14 @@
 					{{svg "octicon-x"}}
 				{{end}}
 			</div>
+			{{if .User.Language}}
+				<div class="flex-item-body">
+					<span class="flex-text-inline">
+						<b>{{ctx.Locale.Tr "settings.language"}}:</b>
+						{{range .AllLangs}}{{if eq $.User.Language .Lang}}{{.Name}}{{end}}{{end}}
+					</span>
+				</div>
+			{{end}}
 			{{if .User.Location}}
 				<div class="flex-item-body">
 					<span class="flex-text-inline">{{svg "octicon-location"}}{{.User.Location}}</span>