Make device attribute optional for subscription requests

[akoshunyadi]

What type of PR is this?

• enhancement/feature

What this PR does / why we need it:

The device attribute in the subscription request has been made optional.

Which issue(s) this PR fixes:

Fixes #189

Special notes for reviewers:

Changelog input

Make device attribute optional for subscription requests

Additional documentation

[bigludo7]

Hi @akoshunyadi
I'm a bit uncomfortable on this one as we must:

• in the notification send back the device identifier
• in the Subscription resource itself have the device identifier in the GET answer (or in POST response)

If we make it optional in the request, it means that the API server will have to get it from the access token and then store it in the subscription resource.
I tend to think that keeping it mandatory makes the thing easier - wdyt?

[akoshunyadi]

@bigludo7 yes, that's a good point! I don't think that we should expose the phone-number from the access token either.

[fernandopradocabrillo]

@akoshunyadi I agree with @bigludo7 on this one, I also prefer to have it required

[akoshunyadi]

As decided in the last sub-project status call, the PR can be closed, see previous comments.