add mail settings to invenio config

[ppanero]

INVENIO_MAIL_NOTIFY_SENDER: InvenioRDM info@inveniordm.com INVENIO_MAIL_SUPPRESS_SEND: 'False' INVENIO_MAIL_SERVER: server.com

[ntarocco]

done, but now removed with https://github.com/inveniosoftware/helm-invenio/pull/59