Update CRD with meaningful set of parameters

[rm3l]

Description

This updates the CRD structure based on the proposal and discussion in #21 (comment), later refined in https://docs.google.com/document/d/14z9tE2XsCRl0hLTbHkyOdv26S6trHLgfpxYOfo-cm1I/edit

This is an example of what we agreed to have:

spec:
  enableLocalDb: true
  application:
    appConfig:
      # All ConfigMaps will be mounted in the same place
      mountPath: "/opt/app-root/src"
      configMaps:
          - name: "my-app-config-cm12"
            # key is optional
            key: "my-file1"
    extraFiles:
      # All ConfigMaps and Secrets will be mounted in the same place
      mountPath: /opt/app-root/src/path/to/my-extra-files
      configMaps:
          - name: "my-extra-config-secret12"
            # key is optional. All files will be mounted if not set
            key: "my-file1"
      secrets:
          - name: "my-extra-config-secret12"
            # key is optional. All files will be mounted if not set
            key: "my-file1"    
    # CM must have a key named 'dynamic-plugins.yaml'
    dynamicPluginsConfigMapName: "my-dynamic-plugins-config-cm"

    extraEnvs:
      configMaps:
        - name: "cm-name"
          # key is optional. Env vars from all keys if key is not set
          key: "key"
      secrets:
        - name: "secret-name"
          # key is optional. Env vars from all keys if key is not set
          key: "key"
      envs:
        - name: MY_ENV_VAR_1
          value: my-value-1
    replicas: 2
    image: "quay.io/rhdh/rhdh-hub-rhel9:1.0-194"
    imagePullSecrets:
      - rhdh-pull-secret

More context in:

• Define (initial) set of spec.parameters for overriding default/raw runtime configuration #21
• Update CRD with initial set of meaningful parameters #26
• https://docs.google.com/document/d/14z9tE2XsCRl0hLTbHkyOdv26S6trHLgfpxYOfo-cm1I/edit

Which issue(s) does this PR fix or relate to

• Fixes Update CRD with initial set of meaningful parameters #26
• Fixes Make it possible to inject user-provided environment variables into the Backstage Deployment #52

PR acceptance criteria

• Tests
• Documentation

How to test changes / Special notes to the reviewer

The most basic CR (with no spec) should work.

See examples of more complete CRs here:

• janus-cr.yaml
• rhdh-cr.yaml

Noteworthy changes:

• app-config files can be mounted under the same mount path (/opt/app-root/src by default)
• extra-config files can be mounted under the same mount path (/opt/app-root/src by default)
• Because dynamic plugins configuration needs to be handled differently from app-configs, the field introduced in Handle app-configs and config for dynamic plugins in Custom Resource #27 is still present. It is now renamed into a simple dynamicPluginsConfigMapName string field.
• The backendAuthSecretRef field introduced in Handle app-configs and config for dynamic plugins in Custom Resource #27 has been removed to make it less confusing. Instead, if user did not specify any appConfig, extraFiles or extraEnv in their CR, we would create a default app-config with a default value for the backend auth key. Otherwise, users are expected to provide their own value for this key (either via their own app-config, or via an APP_CONFIG_... env var)

[rm3l]

We discussed and agreed on the CRD structure: doc

Summarized in #26 (comment)

I'm updating this PR with the new changes..