Command to create SP certificates

[sanathkumarls]

Added a command which will help to create certificates for Service Provider

[pocketnest-erik]

Eager to see this merged!

[sanathkumarls]

@breart this PR is out from very long time, please review. This is a must needed feature.

[breart]

@sanathkumarls it takes one bash command to generate a certificate, why do you need a Laravel command for it?

[sanathkumarls]

@breart it makes developer's life easier.

[breart]

@sanathkumarls I see your point, but I'd argue the generation of certificates, their location, and rotation may be handled differently in companies — it very much depends on the setup of the environment. I see how this feature may benefit some devs, but there is not enough evidence this is going to be used by the majority. I'd rather add a command to the README.