Allow for custom entries in .ssh/config

[noplanman]

In my use-case I connect through a proxy to my backup server, which is defined in the .ssh/config file. The entry that this role generates has fixed contents and I need to create a separate entry especially for the proxy connection.

I'm not sure if it's a good idea to extend the role to allow for this or not.

I was thinking something along the lines of adding a variable borgbackup_custom_ssh_config which would be included as plain text, like:

borgbackup_custom_ssh_config: |
    ProxyCommand nc -x 10.0.1.1:9050 %h %p
    PubkeyAuthentication yes
    # Whatever else might be necessary...

[stroobl]

We can probably support this similar to the port method now. That would be backward compatible.

      Host {{ item.fqdn }}
        StrictHostKeyChecking no
        IdentityFile {{ borgbackup_ssh_key }}
        {% if item.port is defined %}
        Port {{ item.port }}
        {% endif %}
        {% if item.custom_ssh_config is defined %}
        {{ item.custom_ssh_config }}
        {% endif %}

[noplanman]

@stroobl Shall i put together a PR for this then?