feat: allow dot as separator in resource id

[astromechza]

This PR relates to the resource id field in a spec like the following (marked by the arrow below):

apiVersion: score.dev/v1b1
metadata:
  name: example-workload
service:
  ports:
    http:
      port: 8080
...
resources:
  something:
    type: resource-type
    class: default
    id: custom-type              <-----

Currently, this field supports the same character set and syntax as other fields like the workload name, resource type, resource class, etc. In this PR we'd like to change it to also support . as a separator character in order to support resource provisioners that need relate a resource id to a workload.

The example usecase is when we want a resource id to be related to a workload in some way, for example, for example: example-workload.thing would be an identifier for a 'thing' relative to the 'example-workload' workload.

Alternatives

One alternative is to use the resource type, resource class, or a param to indicate this relation to the resource provisioner.

Resource class is not adequate here, because class is a useful provisioner differentiator: the same 'thing' relation could be returned by different classes with different behaviors over the same relation.

Resource param is not adequate here, because the provisioner that provides id: example-workload.thing may not be capable of handling example-workload.other-thing.

Resource type is not adequate here either because the output type structure of the 'thing' is the same for workload-a and workload-b.

Thus it's most natural to encode this as an id.

Shared resources

This also works well in the case of 2 workloads that want to refer to the same 'thing' relation on the example-workload.

flowchart LR
  A[workload-a] --> R("`type: res-type
class: default
id: shared.workload-c.thing`")
  B[workload-b] --> R
  subgraph workload-c
    thing
  end
  R --> thing

Loading

[astromechza]

Note the initial use case here is to provide a new endpoint resource type supported by all Score implementations by default which would use <workload-name>.service.<port-name> to generate the url of a service exposed by another workload.

[chrishumanitec]

LGTM