Display validation errors for file fields on album form

Although we were already displaying the validation errors at the top of
the page, I thought it would be better to also display them against the
relevant form field.

I found the `TailwindFormBuilder` a bit hard to follow and/or customize.
Ultimately I think it would be nice to come up with a tailwind-ified
`file_field` method on the `TailwindFormBuilder`. However, the existing
callsites are already sufficiently different that doing that is a bit
of a challenge.

So the best I could come up with was to make the existing
`TailwindFormBuilder#labels` method public and call that from the form
so that we now display validation errors as part of the label if there
are any, just like we already do for text-like fields. This also means
we can rely on the styles added in the form builder rather than
duplicating them in the form.

I'm not wild about the name of `TailwindFormBuilder#labels` - I assume
it relates to the idea that there is an "error label" as well as the
actual label, but it doesn't read well to me in the form markup. Maybe
`#label_with_errors` would be better?

We might want to consider re-using this on the artist form, but the
styles were sufficiently different and there isn't currently any
validation for the profile picture, so I've left it for now.

app/form_builders/tailwind_form_builder.rb

@@ -58,6 +58,13 @@ def currency_field(object_method, options = {})
     labels + field_wrapper
   end
 
+  def labels(object_method, label_options = {}, field_options = {})
+    label = tailwind_label(object_method, label_options, field_options)
+    error_label = error_label(object_method, field_options)
+
+    @template.content_tag('div', label + error_label, { class: 'flex flex-col items-start' })
+  end
+
   private
 
   def text_like_field(field_method, object_method, options = {})
@@ -75,13 +82,6 @@ def text_like_field(field_method, object_method, options = {})
     labels + field
   end
 
-  def labels(object_method, label_options, field_options)
-    label = tailwind_label(object_method, label_options, field_options)
-    error_label = error_label(object_method, field_options)
-
-    @template.content_tag('div', label + error_label, { class: 'flex flex-col items-start' })
-  end
-
   def tailwind_label(object_method, label_options, field_options)
     text, label_opts = if label_options.present?
                          [label_options[:text], label_options.except(:text)]

app/views/albums/_form.html.erb

@@ -4,7 +4,7 @@
   <%= form.currency_field :price, symbol: '£', class: 'w-full mb-2' %>
   <%= form.text_area :about, rows: 10, class: 'w-full mb-3' %>
   <%= form.text_area :credits, rows: 10, class: 'w-full mb-3' %>
-  <%= form.label :cover %>
+  <%= form.labels :cover %>
   <%= form.file_field :cover, accept: 'image/jpeg,image/png', class: 'block border border-slate-200 mb-3 file:mr-3 file:px-3 file:py-3 w-full file:border-0 file:bg-amber-600 hover:file:bg-amber-500 file:text-white' %>
   <div class="flex items-center gap-2 mb-4">
     <span class="text-amber-600">
@@ -28,9 +28,9 @@
       <%= f.text_field :title, class: 'w-full mb-6', required: true %>
 
       <% if f.object.original.attached? %>
-        <%= f.label :original, "File (#{f.object.original.filename})", class: 'text-slate-600 mb-1 md:mb-0 pr-4' %>
+        <%= f.labels :original, text: "File (#{f.object.original.filename})" %>
       <% else %>
-        <%= f.label :original, "File", class: 'text-slate-600 mb-1 md:mb-0 pr-4' %>
+        <%= f.labels :original, text: "File" %>
       <% end %>
       <%= f.file_field :original, accept: 'audio/x-wav', direct_upload: true, class: 'block border border-slate-200 mb-2 file:mr-3 file:px-3 file:py-3 w-full file:border-0 file:bg-amber-600 hover:file:bg-amber-500 file:text-white' %>
       <div class="progressContainer hidden w-full h-4 bg-slate-200">
@@ -49,7 +49,7 @@
       <%= form.fields_for :tracks, Track.new, child_index: "__CHILD_INDEX__" do |f| %>
       <div class="border-0 border-l-4 border pl-4 mb-6 border-slate-200" >
         <%= f.text_field :title, class: 'w-full mb-6', required: true %>
-        <%= f.label :original, "File", class: 'text-slate-600 mb-1 md:mb-0 pr-4' %>
+        <%= f.labels :original, text: "File" %>
         <%= f.file_field :original, accept: 'audio/x-wav', direct_upload: true, class: 'block border border-slate-200 mb-2 file:mr-3 file:px-3 file:py-3 w-full file:border-0 file:bg-amber-600 hover:file:bg-amber-500 file:text-white' %>
         <div class="progressContainer hidden w-full h-4 bg-slate-200">
           <div class="progress w-0 h-4 bg-slate-500"></div>