API endpoints to manage default delivery channels for customer

[donaldgray]

Allow a customer to manage their own default delivery channels at a customer level.

See docs:

• https://deploy-preview-2--dlcs-docs.netlify.app/api-doc/customer#defaultdeliverychannels

Acceptance Criteria

Support the following verbs:

• GET /customers/{customer}/defaultDeliveryChannels - get customer delivery channel defaults
  • Returns hydra:Collection (of vocab:DeliveryChannel)
  • Returns 200 if found.
  • Returns only defaultDeliveryChannels with space=0
  • If system policy return the name only
  • If non-system policy return fully qualified uri
• POST /customers/{customer}/defaultDeliveryChannels - create customer delivery channel defaults
  • Returns 201 Created on success
  • All fields are required, channel, policy and mediaType
  • The platform will create a GUID for the last path element
  • Creates item with space=0
• GET /customers/{customer}/defaultDeliveryChannels/{id} - get delivery channel default
  • Returns vocab:DeliveryChannel
  • Returns 200 if found.
  • If system policy return the name only
  • If non-system policy return fully qualified uri
• PUT /customers/{customer}/defaultDeliveryChannels/{id} - update delivery channel default
  • Returns 200 on success.
  • Update only, cannot create via PUT
  • id property is GUID generated on POST
  • Can only update space=0 defaults. Cannot change space value
• DELETE /customers/{customer}/defaultDeliveryChannels/{id} - delete delivery channel default
  • Returns 204 NoContent
  • id property is GUID generated on POST
  • Can only delete space=0 defaults.
• There are Playwright tests for all the above

Returned status codes not exhaustive. Standard rules apply for NotFound, BadRequest, InternalServerError etc

[tomcrane]

requires #735

[JackLewis-digirati]

note that this should probably now be Returns hydra:Collection (of vocab:DefaultDeliveryChannel)