SPIKE on restricting options for selecting orgs

app/controllers/account/organisations_controller.rb

@@ -6,6 +6,13 @@ class OrganisationsController < WebController
     skip_before_action :redirect_if_account_not_completed
 
     def edit
+      @organisations = Organisation.for_email(current_user.email).order(:name)
+
+      if @organisations.empty?
+        render :unsupported_email
+        return
+      end
+
       @organisation_input = OrganisationInput.new(user: current_user).assign_form_values
     end
 

app/models/org_domain.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class OrgDomain < ApplicationRecord
+  belongs_to :organisation
+
+  validates :domain, presence: true
+  validates :domain, uniqueness: { scope: :organisation_id, case_sensitive: false }
+
+  before_validation -> { self.domain = domain&.downcase&.strip }
+end

app/models/organisation.rb

@@ -4,6 +4,7 @@ class Organisation < ApplicationRecord
   has_many :groups
   has_many :users
 
+  has_many :org_domains, dependent: :destroy
   has_many :mou_signatures
 
   scope :not_closed, -> { where(closed: false) }
@@ -28,4 +29,13 @@ def as_json(options = {})
     options[:methods] ||= %i[organisation_admin_users]
     super(options)
   end
+
+  def self.for_email(email)
+    domain = email.split('@').last.downcase
+
+    not_closed
+      .joins(:org_domains)
+      .where(org_domains: { domain: domain })
+      .distinct
+  end
 end

app/views/account/organisations/edit.html.erb

@@ -10,7 +10,7 @@
         f,
         attribute_name: :organisation_id,
         form_field: f.govuk_collection_select(:organisation_id,
-                                              Organisation.not_closed.order(:name),
+                                              @organisations,
                                               :id,
                                               :name_with_abbreviation,
                                               class: ['govuk-!-width-three-quarters'],

app/views/account/organisations/unsupported_email.html.erb

@@ -0,0 +1,9 @@
+<div class="govuk-grid-row">
+  <div class="govuk-grid-column-two-thirds">
+    <h1 class="govuk-heading-l">We do not recognise your email address</h1>
+    <p class="govuk-body">
+      Your email address (<%= current_user.email %>) is not associated with a supported organisation.
+    </p>
+    <%= govuk_details(summary_text: t('account.organisation_details_summary'), text: t('account.organisation_text_html', contact_link: contact_link)) %>
+  </div>
+</div>

db/migrate/20260622151619_create_org_domains.rb

@@ -0,0 +1,12 @@
+class CreateOrgDomains < ActiveRecord::Migration[8.1]
+  def change
+    create_table :org_domains do |t|
+      t.references :organisation, null: false, foreign_key: true
+      t.string :domain, null: false
+      t.timestamps
+    end
+
+    add_index :org_domains, [:organisation_id, :domain], unique: true, name: "index_org_domains_unique"
+    add_index :org_domains, :domain
+  end
+end