Document API design guidelines

[shilpa-padgaonkar]

To track #96

[shilpa-padgaonkar]

After merge of PR96, this issue will be closed

[eric-murray]

Reflecting comments I made in the PR to keep this issue up to date, Vodafone would like to see the following changes to the current proposal:

• Inclusion of HTTP status code in any error JSON response (following the approach taken in IETF 7807). This can be optional, and it is accepted that it is not definitive, but for information / post-processing purposes only.
• Filtering notation for >, >=, <, <= should be either replaced by, or at least allow, the TMF notation.

Otherwise, we are happy with the proposed design guidelines.

[jordonezlucena]

Reflecting comments as for #96, the request for changes proposed by VF are acceptable for us. We have updated the .md file accordingly.

[shilpa-padgaonkar]

PR has been merged.

Documentation and related images has been moved to the documentations directory as already clarified with @jordonezlucena and @RubenBG7 . Approved and merged doc can be found here https://github.com/camaraproject/WorkingGroups/blob/main/Commonalities/documentation/API-design-guidelines.md

Closing issue.