ReferentialDecorator: Handle non-`Link` buttons

Referentials#show has a button "Purger" that isn't a link. Instead, it's
a `<button>` element that opens a modal.

Previously, we only knew how to put `Link`s in the `#action_links`, and
only these could then be rendered in the header bar as buttons.

This change allows us to accept non-Link objects. Since the button is
rather simple, I decided to create a simple `HTMLElement` class to
represent it and output it in the resulting HTML. The class uses the
`#content_tag` `ActionView` helper to render the final HTML.

Update "referentials/show.html.slim" to output the button correctly in
addition to the normal links.

Update `TableBuilderHelper#build_links` to not add anything that's not a
`Link` to the gear menu. This allows us to display the "Purger" button
on the Referentials#show page but not in the table on Workbenches#show.

Refs #3479

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/html_element.rb b/lib/html_element.rb
new file mode 100644
index 000000000..469fd7565
--- /dev/null
+++ b/lib/html_element.rb
@@ -0,0 +1,15 @@
+class HTMLElement
+  def initialize(tag_name, content = nil, options = nil)
+    @tag_name = tag_name
+    @content = content
+    @options = options
+  end
+
+  def to_html(options = {})
+    ApplicationController.helpers.content_tag(
+      @tag_name,
+      @content,
+      @options.merge(options)
+    )
+  end
+end