Make ProviderSpec credentialsSecretRef optional

[hasheddan]

Signed-off-by: hasheddan georgedanielmangum@gmail.com

Description of your changes

Makes the credentialsSecretRef field optional in ProviderSpec such that alternative auth methods can be utilized without having to reference a Secret.

Ref: crossplane-contrib/provider-aws#126 (comment)

Checklist

I have:

• Run make reviewable to ensure this PR is ready for review.
• Ensured this PR contains a neat, self documenting set of commits.
• Updated any relevant documentation, examples, or release notes.
• Updated the RBAC permissions in clusterrole.yaml to include any new types.

[upbound-bot]

[negz]

LGTM, but once this is merged I believe every managed resource controller will need to be updated to reflect the changes (e.g. checking whether the ref is now nil).

[hasheddan]

@negz that is correct 👍 I am happy to make those updates. We could also not make it a pointer, then we would just get empty strings and fail to get the secret, but I feel like that would go against our conventions so I would prefer to just make the updates if that sounds good

[negz]

@hasheddan SGTM - I imagine the updates should be fairly mechanical.

[hasheddan]

@negz anything else needed here?

[negz]

Nope - just forgot to hit merge. :)

[hasheddan]

@negz thanks :)