add a caching component to kroki

[oupala]

If you install your own kroki instance following the documentation of kroki, you should end up with an instance of kroki that has no caching capabilities. This means that if you have a webpage somewhere that includes a diagram that is dynamically generated by kroki. If this web page is viewed hundreds of times by numerous users, the diagram is generated hundreds of time for all users. And each diagram generation is identical to the previous and to the next one as the source syntax is identical and as the resulting diagram is also identical.

The prerequisite to caching are already discussed in other issue, such as #1062 and #1083 but I think that the documentation should talk more about caching mechanism. For example, it is easy to use Nginx-Ingress as a Static Cache for Assets Inside Kubernetes as it only require a simple configuration file and can easily be deployed in a docker or a kubernetes environment.

Do you agree that it worth it?

[ggrossetie]

Are we talking about improving the documentation to add information about which headers the Kroki service sets to help with caching, and about possible solutions to implement in order to cache the responses?
If so, yes I think that would be valuable!

[oupala]

Yes, that's the point. I'm willing to get involved in this but I'm sure I don't have all the informations, the skill and the knowledge to do that by myself. I would like to be sure that other people would be interested to join this initiative.