This changes the way the issuer CA is retrieved if no static_ca file is
used. Previously we would always download the CA using the AIA Info but
API v2 provides normally the full chain PEM upon certificate retrieval
and does not need this step. For the APIv2 case we now use the CA
provided with the certificate which required some changes to the basic
handling of CA files. APIv1 has been adapted to this new handling.
APIv2 has a fallback option to the way APIv1 handles it in case no CA
has been provided.
Authorities (e.g. Let's Encrypt) usually have Terms of Serivce (ToS)
that have to be agreed to. Up until this point we automatically
indicated agreement to those ToS and sent the necessary value.
This commit changes the behaviour to be in line with recommendations
from Let's Encrypt that the user themselves have to indicate their
agreement by no longer automatically doing so (except for cases of
legacy configuration files to provide compatibility).
The user can now indicate ToS agreement by either setting the associated
configuration variable (authority_tos_agreement) to the required value
and/or providing the required value via a command-line parameter
(--authority-tos-agreement=<value>/--tos-agreement=<value>/--tos=<value>)
