Add deprecated keyword to OAS for deprecated service (/v1/provide-list-of-connected-devices) (first discuss internally)

[kmohr-soprasteria]

"Problem":
/v1/provide-list-of-connected-devices has been deprecated, but is still to be provided by NEP.
Service currently are only marked as deprecated via lifeCycleState deprecated and possibly a description in the OAS stating that.
(This is also how it was done for RegistryOffice://v1/register-application.)
Note: this is not actually a problem, as the life-cycle-state provides the information about deprecation.

Solution 1:
As long as the service needs to still be served by an application the deprecated keyword could be added.

Note usage of deprecated keyword:

• the keyword is allowed to be used for
  • operations (get, post, etc.)
  • parameters
  • schemas / properties
• this means it cannot be set on service level, but must be there for each operation of the target service (i.e. an own deprecated: true for get, post, delete, etc.)

Solution 2:
Instead of using the deprecated keyword per operation, x-deprecated could be used for the complete service at once.

Next step:
Discuss with Thorsten, if there is any preference on how to mark deprecated services. If deprecated keyword shall be used, this should also be added to any other spec, which contains deprecated services.