Add plugin for hybrid helm operator

[varshaprasad96]

This PR adds a new plugin for hybrid helm operator. It has the scaffolding required for init command.

Usage:
operator-sdk init --plugins=hybrid.helm.sdk.operatorframework.io --project-version="3" --repo=github.com/example/memcached-operator

This scaffolds the following files:

├── Makefile
├── PROJECT
├── config
│   ├── default
│   │   ├── kustomization.yaml
│   │   ├── manager_auth_proxy_patch.yaml
│   │   └── manager_config_patch.yaml
│   ├── manager
│   │   ├── controller_manager_config.yaml
│   │   ├── kustomization.yaml
│   │   └── manager.yaml
│   ├── manifests
│   │   └── kustomization.yaml
│   ├── prometheus
│   │   ├── kustomization.yaml
│   │   └── monitor.yaml
│   ├── rbac
│   │   ├── auth_proxy_client_clusterrole.yaml
│   │   ├── auth_proxy_role.yaml
│   │   ├── auth_proxy_role_binding.yaml
│   │   ├── auth_proxy_service.yaml
│   │   ├── kustomization.yaml
│   │   ├── leader_election_role.yaml
│   │   ├── leader_election_role_binding.yaml
│   │   ├── role.yaml
│   │   ├── role_binding.yaml
│   │   └── service_account.yaml
│   └── scorecard
│       ├── bases
│       │   └── config.yaml
│       ├── kustomization.yaml
│       └── patches
│           ├── basic.config.yaml
│           └── olm.config.yaml
├── go.mod
├── go.sum
├── hack
│   └── boilerplate.go.txt
├── main.go
└── watches.yaml

Note: This scaffolding is when kustomize and scorecard plugins are bundled with hybrid operator plugin. Once this is done, we can either create api using helm or go/v3 plugins.

Ex:
Go plugin:

➜  hybrid-helm-operator: operator-sdk create api --group=cache --version v1alpha1 --kind Memcached --resource --controller --plugins=go/v3
Writing kustomize manifests for you to edit...
Writing scaffold for you to edit...
api/v1alpha1/memcached_types.go
controllers/memcached_controller.go
Update dependencies:
$ go mod tidy
Running make:
$ make generate
go: creating new go.mod: module tmp
Downloading sigs.k8s.io/controller-tools/cmd/controller-gen@v0.4.1
go get: added sigs.k8s.io/controller-tools v0.4.1
/Users/vnarsing/go/src/github.com/example-inc/hybrid-helm-operator/bin/controller-gen object:headerFile="" paths="./..."

Helm plugin:

➜  hybrid-helm-operator: operator-sdk create api --helm-chart=gremlin --helm-chart-repo=https://helm.gremlin.com/ --plugins=helm
Writing kustomize manifests for you to edit...
Created helm-charts/gremlin
Generating RBAC rules
WARN[0001] The RBAC rules generated in config/rbac/role.yaml are based on the chart's default manifest. Some rules may be missing for resources that are only enabled with custom values, and some existing rules may be overly broad. Double check the rules generated in config/rbac/role.yaml to ensure they meet the operator's permission requirements.

The pkg/plugins/hybrid/v1alpha/testdata has been manually generated and added for reference in this PR. A testdata generator script needs to be implemented which writes the scaffolding directly from plugin (instead of wiring it with SDK) in a follow up PR.

[varshaprasad96]

cc: @fabianvf @jmrodri

[coveralls]

Pull Request Test Coverage Report for Build 994610534

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 89.734%

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Totals
Change from base Build 983493779:	0.0%
Covered Lines:	1381
Relevant Lines:	1539

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💛 - Coveralls

[fabianvf]

We want main.go set up such that if you ran create api from the helm plugin we would begin reconciling those resources, which means on init we want to scaffold out the code responsible for loading the watches and setting up the reconcilers. Once that's in there everything else looks good to me

[fabianvf]

I think we also need to copy the helm-charts directory

[fabianvf]

and generally probably need to be closer to the helm-operator base image though that can be a longer term thing

[varshaprasad96]

added the helm chart repository. I have made the entry point to be the manager binary (for now), in a follow up Ill test it out and remove it (as entry point) if not needed.

[fabianvf]

/lgtm
good first pass, needs some followup but this definitely serves as a good POC