fix: version check broken in `exec` and `ssh` commands

Merge pull request aakso#12 from aakso/feat/handle-multiple-cert-vers…

…ions

feat: handle multiple cert versions

Merge pull request aakso#11 from aakso/feat/rsa-stronger-signature-algos

feat: add support for selecting a signing algo for RSA CA keys

feat(build): switch to go 1.17.0

Merge pull request aakso#9 from aakso/feat/challenge-response-ca-add

feat(ca add): implement challenge-response based CA key add

Merge pull request aakso#4 from aakso/go115

Go115

build: add dist target for building inside Docker

server: support multiple TLS certificates

Implemented support for multiple TLS certificates (TLSCertFiles,
TLSKeyFiles, TLSCertNames server configuration options) which allows
a single ssh-inscribe server to properly serve multiple domains.

authoidc: move token validation to callback phase

In some situations it might take quite a lot of time for the auth
provider to respond. Let's move the validation to the callback phase so
that we can continue refreshing the AuthContext by the client.

Also implemented locking with RWMutex and the whole locking less
conservative.

Minor release