Join endpoint_configuration and endpoints into single field and m…

[whites11]

…ake changes to the plan more understandable

Towards: #267

but a general improvement overall.

This PR aims at simplifying and improving the management of endpoints (read protocols) in a clickhouse service in both directions (input or enable/disable and output to get the host and port for each endpoint).

The change is twofold:

1. remove the endpoint_configuration attribute and move endpoint config to the endpoints attribute.
2. change the endpoints attribute from being a list to a map.

Example.

Before this change, to enable the mysql endpoint (the only configurable one) one needed to have this in .tf file

resource "clickhouse_service" "service" {
  ...
  endpoints_configuration = {
    mysql = {
      enabled = true
    }
  }
  ...
}

and the output would have been something like this:

endpoints = [
  {
    protocol = "https"
    host = "ql5ek38hzz.us-east-2.aws.clickhouse.cloud"
    port: 8443
  },
  {
    protocol: "mysql"
    host: "ql5ek38hzz.us-east-2.aws.clickhouse.cloud",
    port: 3306
  },
  ...
]

After this change, users need to use the endpoints field for both enabling the mysql endpoint (and possibly others in the future) and get the hostnames, in a better format like this:

resource "clickhouse_service" "service" {
...
  endpoints = {
    mysql = {
      enabled = true
    }
  }
...
}

and the outputs

endpoints = {
  "https": {
    "host": "ql5ek38hzz.us-east-2.aws.clickhouse.cloud",
    "port": 8443
  },
  "mysql": {
    "enabled": false,
    "host": null,
    "port": null
  },
  "nativesecure": {
    "host": "ql5ek38hzz.us-east-2.aws.clickhouse.cloud",
    "port": 9440
  }
}

the main advantage of this change is that we can have a more fine grained control over the plan when changing endpoint settings, and avoid having all endpoints show up as "known after apply" everytime there was a change.
This has been a rightful request from a few customers.