Add cluster settings api

[nelsonkopliku]

This PR exposes an api at GET /api/clusters/settings to retrieve the clusters settings for the runner to provide to Ansible.

Involved settings are:

• selected checks for a cluster
• hosts for a given cluster with address and user to enable ansible connection

Example API response.

[
    {
        "id": "c115e7ecf5901d9a768d06a28ab0ba26",
        "selected_checks": [],
        "hosts": [
            {
                "name": "vmnetweaver01",
                "address": "x.x.x.x",
                "user": "root"
            },
            {
                "name": "vmnetweaver02",
                "address": "x.x.x.x",
                "user": "root"
            }
        ]
    },
    {
        "id": "5dfbd28f35cbfb38969f9b99243ae8d4",
        "selected_checks": [
            "A",
            "B",
            "C",
        ],
        "hosts": [
            {
                "name": "vmhana01",
                "address": "x.x.x.x",
                "user": "cloudadmin"
            },
            {
                "name": "vmhana02",
                "address": "x.x.x.x",
                "user": "cloudadmin"
            }
        ]
    }
]

This allows the runner to only call one API and provided useful information to Ansible and remove consul dependency from the runner itself (next PR).

[arbulu89]

I have some hard feelings about did.
We already did a huge effort creating the "/checks/:id/settings" group of endpoint for this exact purpose.
This PR in my opinion totally overlaps this.
Did we consider simply adding the connection data information to the currently existing endpoints?
In essence, the information used in the runner, and shown in the frontend is exactly the same

[arbulu89]

I'm super confused with this.
We already have the "/checks/:id/settings" end point for this. Where the id is the ansible group id (as we need to group the ansible checks by group0.
This was named on purpose this way, as we were already seeing high changes to have other checks groups (like SAP system wide checks, or SAP landscapes wide checks)

[dottorblaster]

Mega-LGTM

All the changes have been addressed already and there's team consensous on those