Allow setting the number of claims to allocate

Updates the admin UI providing a select box for allocating a specific
number of claims.

app/views/admin/claims/_allocations_form.html.erb

@@ -1,9 +1,6 @@
-<% allocate_claim_count = @claims.where(assigned_to: nil).count > 25 ? 25 : @claims.where(assigned_to: nil).size %>
-
 <h2 class="govuk-heading-m">Allocate claims</h2>
 
 <%= form_with url: admin_bulk_allocate_path, method: :patch do |form| %>
-  <%= form.hidden_field :allocate_claim_count, value: allocate_claim_count %>
   <div class="govuk-form-group admin-filter-group" id="allocations">
     <div>
       <label class="govuk-label" for="allocate_to_team_member">
@@ -17,10 +14,15 @@
       </label>
       <%= form.select :allocate_to_policy, options_for_select(Policies.options_for_select, params[:policy]), {include_blank: "All"}, class: "govuk-select" %>
     </div>
+    <div>
+      <label class="govuk-label" for="allocate_claim_count">
+        Number of claims:
+      </label>
+      <%= form.select :allocate_claim_count, options_for_select([5, 10, 25], params[:allocate_claim_count] || 25), {}, class: "govuk-select" %>
+    </div>
 
     <div>
-      <div class="govuk-label">Default: 25</div>
-      <%= form.submit "Allocate claims", class: "govuk-button govuk-button--secondary", id: :allocate, disabled: allocate_claim_count.zero? %>
+      <%= form.submit "Allocate claims", class: "govuk-button govuk-button--secondary admin-filter-group__button", id: :allocate, disabled: @claims.where(assigned_to: nil).count.zero? %>
     </div>
 
     <div>

spec/features/admin/admin_claim_allocation_spec.rb

@@ -152,6 +152,36 @@
       expect(page).to have_button "Allocate claims", disabled: false
     end
 
+    scenario "assign 5 claims to one Claim's checker" do
+      click_on "View claims"
+
+      expect(@submitted_claims.size).to eq 40
+
+      select "Frank Yee", from: "allocate_to_team_member"
+      select "All", from: "allocate_to_policy"
+      select "10", from: "allocate_claim_count"
+
+      click_on "Allocate claims"
+
+      within(".govuk-flash__notice") do
+        expect(page).to have_text I18n.t(
+          "admin.allocations.bulk_allocate.success",
+          quantity: 10,
+          pluralized_or_singular_claim: "claims",
+          allocate_to_policy: "",
+          dfe_user: frank.full_name.titleize
+        ).squeeze(" ")
+      end
+
+      @submitted_claims[0..9].each do |claim|
+        expect(claim.reload.assigned_to.full_name).to eq "Frank Yee"
+      end
+
+      @submitted_claims[10..].each do |claim|
+        expect(claim.reload.assigned_to).to be_nil
+      end
+    end
+
     scenario "assign outstanding 10 claims when 25 already allocated" do
       @submitted_claims.slice(0..24).each do |claim|
         claim.assigned_to = @signed_in_user