RPM Support

At time of writing, the documentation for rsync distributors refer to an "auth_type" field in examples. That field is not documented outside of the example and seems to be entirely unused by Pulp.

From https://docs.pulpproject.org/plugins/pulp_rpm/tech-reference/iso-rsync-distributor.html

Here is an example iso_rsync_distributor configuration:

{
    "distributor_id": "my_iso_rsync_distributor",
    "distributor_type_id": "iso_rsync_distributor",
    "distributor_config": {
        "remote": {
            "auth_type": "publickey",
            "ssh_user": "foo",
            "ssh_identity_file": "/home/user/.ssh/id_rsa",
            "host": "192.168.121.1",
            "root": "/home/foo/pulp_root_dir"
        },
        "predistributor_id": "my_iso_distributor"
    }
}

Evidence that auth_type doesn't do anything:

# in pulp - no matches at all
$ git log --oneline -n1; git grep auth_type
0697adee6 (HEAD -> 2-master, origin/2-master) Merge pull request #3571 from goosemania/issue3386

# in pulp_rpm - matches only in these docs
$ git log --oneline -n1; git grep auth_type
eb8a6d0d (HEAD -> 2-master, origin/2-master) Merge pull request #1157 from dparalen/issue_3256
docs/tech-reference/iso-rsync-distributor.rst:                "auth_type": "publickey",
docs/tech-reference/rsync-distributor.rst:                "auth_type": "publickey",

Steps to reproduce¶

Read Pulp documentation for rsync distributors.

Actual behavior¶

Documentation refers to options which don't exist.

Expected behavior¶

Documentation refers only to options which exist.