Add CRUD API unit tests for VLAN network
Add default values for GlobalConfiguration
Add CRUD API unit tests for Global Configuration
Adjust LAGG resource

- Do not allow update
- Remove unnecessary attributes
Assign LAGG form instance attribute correctly
Add CRUD API unit tests for LAGG interface
Add CRUD API unit tests for system Settings
Add CRID API unit tests for Advanced settings
Add CRUD API unit tests for Email
Use DatasetResource as a nested resource of volume
Use a generic way to dispatch nested resource

This will avoid some code duplication.
Implement dataset resource to create and delete
Do not register dataset as a main resource
Make confirm password optional, default on
Add extra method in bsdUsers resource to change password
Fix missing imports

While I'm here do some PEP8 cleanup.
Add API unit test for user password change
Fix iSCSI global configuration form validation

While I'm here fix model default value for auth method.
Add CRUD API unit tests for iSCSI Global Configuration
Rename extent form fields for consistency