Credentials API specification extended.
Credentials API specification extended.

The secrets array in the Credentials Format section is now demanded to
contain at least one element.

Signed-off-by: Karsten Frank <22534dcdeefa21bf02bac7694b065eeae56646bb@bosch-si.com>

kinbod/hono,dejanb/hono,dejanb/hono,dejanb/hono,kinbod/hono,kinbod/hono