ProviderConfig externalID should take a secretRef

[anthonynashduco]

What problem are you facing?

We use an external-id to assume through our auth account into other accounts. This value is, and should be treated as, a secret. Currently in the ProviderConfig you can only hard code a value into the resource, which is a problem when they're in gitops.

What could help solve your problem?

Change structure from

spec:
  assumeRoleChain:
  - externalID: <string>

to

spec:
  assumeRoleChain:
  - externalID:
      secretRef:            # Either this
        name: <string>
        namespace: <string>
        key: <string>
      value: <string>       # or this