Possibility to configure RestAPI caching operations.

[folix-01]

Change the negotiation order for caching operations ruleset for RestAPI Services

[mister-roboto]

@folix-01 thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[folix-01]

@jenkins-plone-org please run jobs

[folix-01]

plone/plone.app.caching#143

[davisagli]

@folix-01 @cekk It is already possible to associate a cache ruleset with a specific REST service in ZCML, like this:

https://github.com/plone/plone.restapi/blob/682567a86b9fc022fbad32e27906475c5410eee1/src/plone/restapi/services/multilingual/configure.zcml#L26-L28

Is it really necessary to add another way to do it? If not I'd prefer to keep things simpler.

Also, this is a low-level package that must not have a hard dependency on anything from plone.app.*. So it's a problem to import from plone.app.caching without making it conditional. (To put it in other words: It must remain possible to create a Plone site that has plone.rest installed but not plone.app.caching.)