[db/v1/instances] add access field - trove database dbaas

[zhekazuev]

Issue

Fixes #2878

Description

• code: add AccessOpts struct
• code: reuse AccessOpts for Access field in CreateOpts - like a value, not pointer - OK?
• code: add non-empty checking for that field - OK?
• tests: add field to testing/fixtures_test.go
• tests: add field to testing/requests_test.go
• tests: add link to api-ref samples

Links

• Service/
  ‎InstanceController.create: https://github.com/openstack/trove/blob/40fdb7b44fb33e022b77ba8df63fde2565c70dea/trove/instance/service.py#L366
• Service/models.Instance.create: https://github.com/openstack/trove/blob/40fdb7b44fb33e022b77ba8df63fde2565c70dea/trove/instance/service.py#L494
• Service/
  ‎InstanceController.update: https://github.com/openstack/trove/blob/40fdb7b44fb33e022b77ba8df63fde2565c70dea/trove/instance/service.py#L581

Related:

• Grant database access to user #2830
• trove: Add Grant and Revoke database access feature #2831
• https://github.com/openstack/trove/blob/4de40cb5144cfd8cdc4b270f23acfdbd3eafa5be/api-ref/source/instances.inc#create-database-instance
• https://github.com/openstack/trove/blob/4de40cb5144cfd8cdc4b270f23acfdbd3eafa5be/api-ref/source/instances.inc#show-database-instance-details

[coveralls]

coverage: 77.835%. remained the same
when pulling 97d56c7 on zhekazuev:feature/add-db-instance-access-field
into 8587253 on gophercloud:master.

[zhekazuev]

@EmilienM Hi,

What better to use for Access field, a pointer(*AccessOpts) or a value(AccessOpts)?
Commit with changes: 0b8b1e1

From the risks and style side.
I prefer to not use pointers where possible, to avoid null pointer issues, but maybe for current scenario there is no option with a value.

[zhekazuev]

@EmilienM Hi,

What better to use for Access field, a pointer(*AccessOpts) or a value(AccessOpts)? Commit with changes: 0b8b1e1

From the risks and style side. I prefer to not use pointers where possible, to avoid null pointer issues, but maybe for current scenario there is no option with a value.

@EmilienM Hi,

Could you review these changes?

I just added new field - Access. Without methods specific for that field, e.g.:

• UpdateInstanceAccessbility - update access options like here.

And decided to use the value for Access struct instead of pointers as described below.
If it is important to use pointers, I can restore the changes to the pointer version.