Allow configuring textarea input options (#2665)

This allows configuring the rendered `<textarea>` for `Field::Text`
fields, e.g.:

    ATTRIBUTE_TYPES = {
      body: Field::Text.with_options(input_options: { rows: 20 }),
    }.freeze

Will render:

    <textarea rows="20" name="post[body]" id="post_body">...</textarea>

app/views/fields/text/_form.html.erb

@@ -18,5 +18,5 @@ This partial renders a textarea element for a text attribute.
   <%= f.label field.attribute %>
 </div>
 <div class="field-unit__field">
-  <%= f.text_area field.attribute %>
+  <%= f.text_area field.attribute, field.options.fetch(:input_options, {}) %>
 </div>

docs/customizing_dashboards.md

@@ -267,6 +267,9 @@ Default is `false`.
 `:truncate` - Set the number of characters to display in the index view.
 Defaults to `50`.
 
+`:input_options` - Options to customize the text area in form view.
+Example: `.with_options(input_options: { rows: 20 })`
+
 **Field::Url**
 
 `:searchable` - Specify if the attribute should be considered when searching.

spec/administrate/views/fields/text/_form_spec.rb

@@ -0,0 +1,56 @@
+require "rails_helper"
+require "administrate/field/text"
+
+RSpec.describe "fields/text/_form", type: :view do
+  it "allows configuring input options" do
+    textarea = instance_double(
+      "Administrate::Field::Text",
+      attribute: :name,
+      data: nil,
+      options: {input_options: {rows: 50}}
+    )
+
+    render_partial(textarea)
+
+    expect(rendered).to have_css(%(textarea[rows=50]))
+  end
+
+  it "doesn't require input options" do
+    textarea = instance_double(
+      "Administrate::Field::Text",
+      attribute: :name,
+      data: nil,
+      options: {}
+    )
+
+    render_partial(textarea)
+
+    expect(rendered).to have_css(%(textarea))
+  end
+
+  def render_partial(field)
+    product = build(:product)
+
+    render(
+      partial: "fields/text/form",
+      locals: {field: field, f: form_builder(product)}
+    )
+  end
+
+  def form_builder(object)
+    ActionView::Helpers::FormBuilder.new(
+      object.model_name.singular,
+      object,
+      build_template,
+      {}
+    )
+  end
+
+  def build_template
+    Object.new.tap do |template|
+      template.extend ActionView::Helpers::FormHelper
+      template.extend ActionView::Helpers::FormOptionsHelper
+      template.extend ActionView::Helpers::FormTagHelper
+    end
+  end
+end