Parameterised matrix test for each Vendor

[mickenordin]

Parameterised matrix test for each Vendor V (V to/from Stub, V to/from V, Stub to/from Stub), where the “Stub” is an OCM stub implementation provided by https://github.com/cs3org/ocm-stub that is to be considered the reference implementation of the protocol.

[MahdiBaghbani]

Modifying OCM stub to generate invite token and also accept the invite token from CERNBox:

• feat: implement invite token generation and acceptance flow OCM-stub#14

For Nextcloud:

• Add OCM Test Suite matrix workflow for Nextcloud nextcloud/server#57274
• A demo of the run can be found in the GitHub Actions

For CERNBox:

• Add OCM Test Suite matrix workflow for CERNBox reva#5458
• A demo of the run can be found in the GitHub Actions

For OCM Test Suite to handle running inside the Vendor CI and do the orchestration of the tests:

• add: Nextcloud and CERNBox sepcific CI actions ocm-test-suite#214