feat(hook): support for hook in nfs-provisioner

[mynktl]

Why is this PR required? What issue does it fix?:
This PR implements hooks to configure nfs resources on provisioning and delete.

What this PR does?:
This PR adds support to execute hook on NFS resources during provisioning events.
To enable hook execution, nfs-provisioner needs to be configured with env var
OPENEBS_IO_NFS_HOOK_CONFIGMAP set to hook Configmap created in nfs-provisioner namespace.

Hook config data must be set under a field named config.

Sample Hook config is as below:

apiVersion: v1
kind: ConfigMap
metadata:
  name: hook-config
  namespace: openebs
data:
  config: |
    hooks:
      addOrUpdateEntriesOnCreateVolumeEvent:
        backendPV:
          annotations:
            example.io/track: "true"
            test.io/owner: teamA
            test.io/tracking-create-time: $current-time
          finalizers:
          - test.io/tracking-protection
        backendPVC:
          annotations:
            example.io/track: "true"
            test.io/owner: teamA
          finalizers:
          - test.io/tracking-protection
        name: createHook
        nfsDeployment:
          annotations:
            example.io/track: "true"
            test.io/owner: teamA
          finalizers:
          - test.io/tracking-protection
        nfsPV:
          annotations:
            example.io/track: "true"
            test.io/owner: teamA
          finalizers:
          - test.io/tracking-protection
        nfsService:
          annotations:
            example.io/track: "true"
            test.io/owner: teamA
          finalizers:
          - test.io/tracking-protection
      removeEntriesOnDeleteVolumeEvent:
        backendPV:
          finalizers:
          - test.io/tracking-protection
        backendPVC:
          finalizers:
          - test.io/tracking-protection
        name: deleteHook
        nfsDeployment:
          finalizers:
          - test.io/tracking-protection
        nfsPV:
          finalizers:
          - test.io/tracking-protection
        nfsService:
          finalizers:
          - test.io/tracking-protection
    version: 1.0.0

Ref:

• Design document for hooks

Does this PR require any upgrade changes?:
No

If the changes in this PR are manually verified, list down the scenarios covered::

Checklist:

• Fixes #
• PR Title follows the convention of <type>(<scope>): <subject>
• Has the change log section been updated?
• Commit has unit tests
• Commit has integration tests
• (Optional) Does this PR change require updating NFS-Provisioner Chart? If yes, mention the Helm Chart PR chore(chart-hook): updating chart to configure hooks for nfs-provisioner #97
• (Optional) Are upgrade changes included in this PR? If not, mention the issue/PR to track:
• (Optional) If documentation changes are required, which issue on https://github.com/openebs/openebs-docs is used to track them:

[codecov-commenter]

Codecov Report

Merging #93 (f153dcc) into develop (75dc272) will increase coverage by 2.77%.
The diff coverage is 71.06%.

@@             Coverage Diff             @@
##           develop      #93      +/-   ##
===========================================
+ Coverage    47.11%   49.88%   +2.77%     
===========================================
  Files           29       38       +9     
  Lines         2390     2700     +310     
===========================================
+ Hits          1126     1347     +221     
- Misses        1185     1250      +65     
- Partials        79      103      +24     

Impacted Files	Coverage Δ
provisioner/env.go	30.00% <0.00%> (-3.34%)	⬇️
provisioner/helper_kernel_nfs_server.go	71.42% <0.00%> (-8.29%)	⬇️
provisioner/provisioner.go	0.00% <0.00%> (ø)
provisioner/provisioner_kernel_nfs_server.go	0.00% <0.00%> (ø)
pkg/hook/execute.go	60.49% <60.49%> (ø)
pkg/helper/helper.go	100.00% <100.00%> (ø)
pkg/hook/action.go	100.00% <100.00%> (ø)
pkg/hook/deployment_action.go	100.00% <100.00%> (ø)
pkg/hook/helper.go	100.00% <100.00%> (ø)
pkg/hook/parser.go	100.00% <100.00%> (ø)
... and 12 more

---

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[mittachaitu]

Provided few comments.. moreover it looks good

[mittachaitu]

changes are good

[mittachaitu]

can we update the example in the description (provisioingingEvent --> eventType, hookAction --> actionType and corresponding values)?

[mittachaitu]

changes look good but there is a small comment about naming conventions

[mittachaitu]

changes are good

[kmova]

Looks good for initial implementation and to follow up with integration tests that cover scenarios like handling provisioning cases that don't go till the point of successfully creating and adding hooks.