Add template linting via djlint (#25212)

So I found this [linter](https://github.com/Riverside-Healthcare/djlint)
which features a mode for go templates, so I gave it a try and it did
find a number of valid issue, like unbalanced tags etc. It also has a
number of bugs, I had to disable/workaround many issues.

Given that this linter is written in python, this does add a dependency
on `python` >= 3.8 and `poetry` to the development environment to be
able to run this linter locally.

- `e.g.` prefixes on placeholders are removed because the linter had a
false-positive on `placeholder="e.g. cn=Search"` for the `attr=value`
syntax and it's not ideal anyways to write `e.g.` into a placeholder
because a placeholder is meant to hold a sample value.
- In `templates/repo/settings/options.tmpl` I simplified the logic to
not conditionally create opening tags without closing tags because this
stuff confuses the linter (and possibly the reader as well).

templates/repo/settings/webhook/base_list.tmpl

@@ -50,7 +50,7 @@
 			<div class="item truncated-item-container">
 				<span class="text {{if eq .LastStatus 1}}green{{else if eq .LastStatus 2}}red{{else}}grey{{end}} gt-mr-3">{{svg "octicon-dot-fill" 22}}</span>
 				<a class="text truncate gt-f1 gt-mr-3" title="{{.URL}}" href="{{$.BaseLink}}/{{.ID}}">{{.URL}}</a>
-				<a class="muted gt-p-3" href="{{$.BaseLink}}/{{.ID}}">{{svg "octicon-pencil"}}</a></span>
+				<a class="muted gt-p-3" href="{{$.BaseLink}}/{{.ID}}">{{svg "octicon-pencil"}}</a>
 				<a class="delete-button gt-p-3" data-url="{{$.Link}}/delete" data-id="{{.ID}}">{{svg "octicon-trash"}}</a>
 			</div>
 		{{end}}

templates/repo/settings/webhook/discord.tmpl

@@ -8,11 +8,11 @@
 		</div>
 		<div class="field">
 			<label for="username">{{.locale.Tr "repo.settings.discord_username"}}</label>
-			<input id="username" name="username" value="{{.DiscordHook.Username}}" placeholder="e.g. Gitea">
+			<input id="username" name="username" value="{{.DiscordHook.Username}}" placeholder="Gitea">
 		</div>
 		<div class="field">
 			<label for="icon_url">{{.locale.Tr "repo.settings.discord_icon_url"}}</label>
-			<input id="icon_url" name="icon_url" value="{{.DiscordHook.IconURL}}" placeholder="e.g. https://example.com/assets/img/logo.svg">
+			<input id="icon_url" name="icon_url" value="{{.DiscordHook.IconURL}}" placeholder="https://example.com/assets/img/logo.svg">
 		</div>
 		{{template "repo/settings/webhook/settings" .}}
 	</form>

templates/repo/settings/webhook/history.tmpl

@@ -3,8 +3,7 @@
 		{{.locale.Tr "repo.settings.recent_deliveries"}}
 		{{if .Permission.IsAdmin}}
 			<div class="ui right">
-				<button class="ui teal tiny button" id="test-delivery" data-tooltip-content=
-				"{{.locale.Tr "repo.settings.webhook.test_delivery_desc"}}" data-link="{{.Link}}/test" data-redirect="{{.Link}}">{{.locale.Tr "repo.settings.webhook.test_delivery"}}</button>
+				<button class="ui teal tiny button" id="test-delivery" data-tooltip-content="{{.locale.Tr "repo.settings.webhook.test_delivery_desc"}}" data-link="{{.Link}}/test" data-redirect="{{.Link}}">{{.locale.Tr "repo.settings.webhook.test_delivery"}}</button>
 			</div>
 		{{end}}
 	</h4>

templates/repo/settings/webhook/packagist.tmpl

@@ -4,15 +4,15 @@
 		{{.CsrfTokenHtml}}
 		<div class="required field {{if .Err_Username}}error{{end}}">
 			<label for="username">{{.locale.Tr "repo.settings.packagist_username"}}</label>
-			<input id="username" name="username" value="{{.PackagistHook.Username}}" placeholder="e.g. Gitea" autofocus required>
+			<input id="username" name="username" value="{{.PackagistHook.Username}}" placeholder="Gitea" autofocus required>
 		</div>
 		<div class="required field {{if .Err_APIToken}}error{{end}}">
 			<label for="api_token">{{.locale.Tr "repo.settings.packagist_api_token"}}</label>
-			<input id="api_token" name="api_token" value="{{.PackagistHook.APIToken}}" placeholder="e.g. X5F_tZ-Wj3c1vqaU2Rky" required>
+			<input id="api_token" name="api_token" value="{{.PackagistHook.APIToken}}" placeholder="X5F_tZ-Wj3c1vqaU2Rky" required>
 		</div>
 		<div class="required field {{if .Err_PackageURL}}error{{end}}">
 			<label for="package_url">{{.locale.Tr "repo.settings.packagist_package_url"}}</label>
-			<input id="package_url" name="package_url" value="{{.PackagistHook.PackageURL}}" placeholder="e.g. https://packagist.org/packages/laravel/framework" required>
+			<input id="package_url" name="package_url" value="{{.PackagistHook.PackageURL}}" placeholder="https://packagist.org/packages/laravel/framework" required>
 		</div>
 		{{template "repo/settings/webhook/settings" .}}
 	</form>

templates/repo/settings/webhook/slack.tmpl

@@ -8,20 +8,20 @@
 		</div>
 		<div class="required field {{if .Err_Channel}}error{{end}}">
 			<label for="channel">{{.locale.Tr "repo.settings.slack_channel"}}</label>
-			<input id="channel" name="channel" value="{{.SlackHook.Channel}}" placeholder="e.g. #general" required>
+			<input id="channel" name="channel" value="{{.SlackHook.Channel}}" placeholder="#general" required>
 		</div>
 
 		<div class="field">
 			<label for="username">{{.locale.Tr "repo.settings.slack_username"}}</label>
-			<input id="username" name="username" value="{{.SlackHook.Username}}" placeholder="e.g. Gitea">
+			<input id="username" name="username" value="{{.SlackHook.Username}}" placeholder="Gitea">
 		</div>
 		<div class="field">
 			<label for="icon_url">{{.locale.Tr "repo.settings.slack_icon_url"}}</label>
-			<input id="icon_url" name="icon_url" value="{{.SlackHook.IconURL}}" placeholder="e.g. https://example.com/img/favicon.png">
+			<input id="icon_url" name="icon_url" value="{{.SlackHook.IconURL}}" placeholder="https://example.com/img/favicon.png">
 		</div>
 		<div class="field">
 			<label for="color">{{.locale.Tr "repo.settings.slack_color"}}</label>
-			<input id="color" name="color" value="{{.SlackHook.Color}}" placeholder="e.g. #dd4b39, good, warning, danger">
+			<input id="color" name="color" value="{{.SlackHook.Color}}" placeholder="#dd4b39, good, warning, danger">
 		</div>
 		{{template "repo/settings/webhook/settings" .}}
 	</form>