Add DAO function and endpoint for archiving letter contact blocks

Added a new DAO function which archives letter contact blocks by
setting archived to True. This raises an ArchiveValidationError if
trying to archive the default letter block for a service or the default
letter contact block for a template.

Added a new endpoint for archiving letter contact blocks.

app/dao/service_letter_contact_dao.py

@@ -3,7 +3,8 @@ from sqlalchemy import desc
 from app import db
 from app.dao.dao_utils import transactional
 from app.errors import InvalidRequest
-from app.models import ServiceLetterContact
+from app.exceptions import ArchiveValidationError
+from app.models import ServiceLetterContact, Template
 
 
 def dao_get_letter_contacts_by_service_id(service_id):
@@ -65,6 +66,32 @@ def update_letter_contact(service_id, letter_contact_id, contact_block, is_defau
     return letter_contact_update
 
 
+@transactional
+def archive_letter_contact(service_id, letter_contact_id):
+    letter_contact_to_archive = ServiceLetterContact.query.filter_by(
+        id=letter_contact_id,
+        service_id=service_id
+    ).one()
+
+    if _is_template_default(letter_contact_id):
+        raise ArchiveValidationError("You cannot delete the default letter contact block for a template")
+    if letter_contact_to_archive.is_default:
+        raise ArchiveValidationError("You cannot delete a default letter contact block")
+
+    letter_contact_to_archive.archived = True
+
+    db.session.add(letter_contact_to_archive)
+    return letter_contact_to_archive
+
+
+def _is_template_default(letter_contact_id):
+    template_defaults = Template.query.filter_by(
+        service_letter_contact_id=letter_contact_id
+    ).all()
+
+    return any(template_defaults)
+
+
 def _get_existing_default(service_id):
     letter_contacts = dao_get_letter_contacts_by_service_id(service_id=service_id)
     if letter_contacts:

app/service/rest.py

@@ -59,6 +59,7 @@ from app.dao.service_email_reply_to_dao import (
     update_reply_to_email_address
 )
 from app.dao.service_letter_contact_dao import (
+    archive_letter_contact,
     dao_get_letter_contacts_by_service_id,
     dao_get_letter_contact_by_id,
     add_letter_contact_for_service,
@@ -638,6 +639,13 @@ def update_service_letter_contact(service_id, letter_contact_id):
     return jsonify(data=new_reply_to.serialize()), 200
 
 
+@service_blueprint.route('/<uuid:service_id>/letter-contact/<uuid:letter_contact_id>/archive', methods=['POST'])
+def delete_service_letter_contact(service_id, letter_contact_id):
+    archived_letter_contact = archive_letter_contact(service_id, letter_contact_id)
+
+    return jsonify(data=archived_letter_contact.serialize()), 200
+
+
 @service_blueprint.route('/<uuid:service_id>/sms-sender', methods=['POST'])
 def add_service_sms_sender(service_id):
     dao_fetch_service_by_id(service_id)