docs: add infos how to add ttl of JWT-tokens in the response

[Chris53897]

docs: add infos how to add ttl of JWT-tokens in response of the authentication endpoint. add automated authentication with JWT in postman.

I am not sure if it is ok to generate a new page for postman. But later there could be added an example with OAuth2 or other postman related infos. The JWT page is already very big.

I guess markdown linter will fail because the jwt page uses non valid data before.