create and edit cluster policy / accept real dict for definition instead of pure string

[copdips]

The API needs a pure string with espace on quotes for the value of the definition key:
https://docs.databricks.com/dev-tools/api/latest/policies.html#example

it would be nice in databricks cluster-policies [create|edit], in the given json file, if the value of the definition key is a dict, then databricks-cli converts it to a pure string directly with escape. because adding quotes escape is not easy, and especially when saving the code in git, a definition in pure string is very unreadable,

hereunder, an example of pure dict policy, but we need to pre-convert the definition part to string.

{
  "policy_id": "foo",
  "name": "bar",
  "definition": {
    "cluster_type": {
      "type": "fixed",
      "value": "job"
    }
}

[pietern]

@copdips That sounds reasonable. Would you want to submit a PR for this?

[copdips]

ok by this weekend

[pietern]

@copdips That's great, thank you. And there's no rush, so whatever is convenient.

Happy to work with you on getting this feature in.

[copdips]

resolved by #557