add secrets for login salt and secret key

[ppanero]

            - name: INVENIO_SECRET_KEY
              valueFrom:
                secretKeyRef:
                  name: invenio-secrets
                  key: INVENIO_SECRET_KEY
            - name: INVENIO_SECURITY_LOGIN_SALT
              valueFrom:
                secretKeyRef:
                  name: invenio-secrets
                  key: INVENIO_SECURITY_LOGIN_SALT

And the corresponding secret creation

[ntarocco]

Already done, closing.