Introduce entrypoint to enable working with relative path modules

[ytsarev]

Description of your changes

Fixes #83

Signed-off-by: Yury Tsarev yury@upbound.io

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Used https://github.com/ytsarev/provider-terraform-test-module for e2e testing

$ cat tf.yaml
apiVersion: tf.crossplane.io/v1alpha1
kind: Workspace
metadata:
  name: relative-path-test
spec:
  forProvider:
    module: git::https://github.com/ytsarev/provider-terraform-test-module.git
    source: Remote
    entrypoint: relative-path-iam
    vars:
      - key: iamRole
        value: relative-path-test

$ cat tf-regression.yaml
apiVersion: tf.crossplane.io/v1alpha1
kind: Workspace
metadata:
  name: regression-test
spec:
  forProvider:
    module: git::https://github.com/ytsarev/provider-terraform-test-module.git//iam?ref=main
    source: Remote
    vars:
      - key: iamRole
        value: regression-test

k apply -f tf.yaml

k apply -f tf-regression.yaml

k get -f tf-regression.yaml
NAME              READY   SYNCED   AGE
regression-test   True    True     4m52s

k get -f tf.yaml
NAME                 READY   SYNCED   AGE
relative-path-test   True    True     4m52s

[bobh66]

LGTM - maybe add a section in the README with a brief description of the scenario where entrypoint is used?

[ytsarev]

@bobh66 thanks a lot for the review, PR amended with the README extension 👍