Update API-design-guidelines for subscription

[bigludo7]

What type of PR is this?

Add one of the following kinds:

• enhancement/feature

What this PR does / why we need it:

Reformulate the subscription part to align with our decision to move to CloudsEvent subscription model. This PR is aligned with the PR #189 which provide an examples.

Which issue(s) this PR fixes:

Fixes #185 #153 #149 #140

Special notes for reviewers:

Changelog input

 release-note
- Move to cloudsEvents subscription model
- Add `initialevent` management
- Add draft subscription status management

Additional documentation

This section can be blank.

docs

[AxelNennker]

I changed my mind about ACCESSTOKEN. There is not much Camara can do on enforcing security at the API consumer. Somebody can please resolve the conversations. @shilpa-padgaonkar

[bigludo7]

I changed my mind about ACCESSTOKEN. There is not much Camara can do on enforcing security at the API consumer. Somebody can please resolve the conversations. @shilpa-padgaonkar

Thanks @AxelNennker @PedroDiez I can close this point?

[shilpa-padgaonkar]

@bigludo7 Thanks. There is another very small fix already proposed as suggestion in this comment by Axel https://github.com/camaraproject/Commonalities/pull/198#discussion_r1615869708 which will fix the missing authZ header in one of the examples. After that its /LGTM :)

[bigludo7]

Thanks @shilpa-padgaonkar for the pointer on @AxelNennker comment. Commited!

[shilpa-padgaonkar]

@bigludo7 I noticed that there is a minor conflict you would need to resolve in the file which is blocking the merge. If you could kindly do this, we would go ahead and merge this PR as we have enough approvals now :)

[bigludo7]

@bigludo7 I noticed that there is a minor conflict you would need to resolve in the file which is blocking the merge. If you could kindly do this, we would go ahead and merge this PR as we have enough approvals now :)

Thanks @shilpa-padgaonkar. Hope to have fixed it.