Add Set object's legalhold status api

[cesnietor]

Status can be set to either 'enabled' or 'disabled':
Api PUT on /api/v1/buckets/<bucket_name>/objects/legalhold?prefix=<file_path>&version_id=<file_version>
Request payload example:

{
    "status": "disabled"
}

After a successful response you can do get on list objects and the status should be reflected there e.g.:
GET on /api/v1/buckets/<bucket_name>/objects?prefix=<file_path>&with_versions=true

{
    "objects": [
        {
            "is_latest": true,
            "last_modified": "2020-10-14 21:54:00.842 +0000 UTC",
            "legal_hold_status": "ON",
            "name": "<file>",
            "size": 19822527,
            "version_id": "<version>"
        },
       ...
}

• Tests included

[Alevsk]

LGTM