Allow constant values in service.binding/name annotations in CRD

[johnpoth]

It would be cool to allow constant values in annotations so something like

service.binding/provider: postgresql

For example, the provider and type entries are recommended and can be the same across all underlying CR which warrants them to be constants. This also facilitates ad-hoc fixes. Thanks !

[pedjak]

We follow the annotation format defined here, and it does not support something like this at the moment. Perhaps worth proposing it?

In the meantime, we can achieve the same result by defining a mapping:

mappings:
   - name: provider
     value: postgresql    

[johnpoth]

Thanks @pedjak for the workaround! Proposed the enhancement

[pedjak]

Also, with #985 it is possible to specify .type and .provider directly on service binding resource.