Merchants improvements (#594)

* FIX logos

* Implement merchant mods

* FIX confirm issue

* FIX linter

* Add recently seen merchants to re-add if needed

* Update merge.html.erb

* FIX do security check

* Add error handling for update failures.

app/models/provider_merchant.rb

@@ -3,4 +3,34 @@ class ProviderMerchant < Merchant
 
   validates :name, uniqueness: { scope: [ :source ] }
   validates :source, presence: true
+
+  # Convert this ProviderMerchant to a FamilyMerchant for a specific family.
+  # Only affects transactions belonging to that family.
+  # Returns the newly created FamilyMerchant.
+  def convert_to_family_merchant_for(family, attributes = {})
+    transaction do
+      family_merchant = family.merchants.create!(
+        name: attributes[:name].presence || name,
+        color: attributes[:color].presence || FamilyMerchant::COLORS.sample,
+        logo_url: logo_url,
+        website_url: website_url
+      )
+
+      # Update only this family's transactions to point to new merchant
+      family.transactions.where(merchant_id: id).update_all(merchant_id: family_merchant.id)
+
+      family_merchant
+    end
+  end
+
+  # Unlink from family's transactions (set merchant_id to null).
+  # Does NOT delete the ProviderMerchant since it may be used by other families.
+  # Tracks the unlink in FamilyMerchantAssociation so it shows as "recently unlinked".
+  def unlink_from_family(family)
+    family.transactions.where(merchant_id: id).update_all(merchant_id: nil)
+
+    # Track that this merchant was unlinked from this family
+    association = FamilyMerchantAssociation.find_or_initialize_by(family: family, merchant: self)
+    association.update!(unlinked_at: Time.current)
+  end
 end