Replace the input! macro with an Input builder (#646)

* Replace the input! macro with an Input builder

* Use a BTreeMap instead of an HashMap

Followinf @fdb-hiroshima's advice

* Rename Input::to_html to Input::html

To make clippy happy

* Wrap error messages in red paragraphs

templates/posts/new.rs.html

@@ -25,8 +25,15 @@
     } else {
 	    <form id="plume-fallback-editor" class="new-post" method="post" action="@uri!(posts::new: blog = blog.actor_id)" content-size="@content_len">
     }
-        @input!(ctx.1, title (text), "Title", form, errors.clone(), "required")
-        @input!(ctx.1, subtitle (optional text), "Subtitle", form, errors.clone(), "")
+        @(Input::new("title", i18n!(ctx.1, "Title"))
+            .default(&form.title)
+            .error(&errors)
+            .html(ctx.1))
+        @(Input::new("subtitle", i18n!(ctx.1, "Subtitle"))
+            .default(&form.subtitle)
+            .error(&errors)
+            .optional()
+            .html(ctx.1))
 
         @if let Some(ValidationErrorsKind::Field(errs)) = errors.clone().errors().get("content") {
             @format!(r#"<p class="error">{}</p>"#, errs[0].message.clone().unwrap_or_else(|| Cow::from("Unknown error")))
@@ -40,9 +47,17 @@
             <a href="@uri!(medias::new)">@i18n!(ctx.1, "Upload media")</a>
         </p>
 
-        @input!(ctx.1, tags (optional text), "Tags, separated by commas", form, errors.clone(), "")
-
-        @input!(ctx.1, license (optional text), "License", "Leave it empty to reserve all rights", form, errors, "")
+        @(Input::new("tags", i18n!(ctx.1, "Tags, separated by commas"))
+            .default(&form.tags)
+            .error(&errors)
+            .optional()
+            .html(ctx.1))
+        @(Input::new("license", i18n!(ctx.1, "License"))
+            .default(&form.license)
+            .error(&errors)
+            .optional()
+            .details("Leave it empty to reserve all rights")
+            .html(ctx.1))
 
         @:image_select(ctx, "cover", i18n!(ctx.1, "Illustration"), true, medias, form.cover)