Add persistence layer

Dealing with a server restart isn't a big deal for simple deployments of Toxiproxy with a couple proxies and toxics. However, as the environment grows to dozens of proxies things become problematic as a restart will take down every API until they are all setup again. The /populate endpoint takes care of a lot of this since it can be called when starting, but someone needs to maintain that JSON array.

I would like to propose a persistence layer that will save all proxies and toxics and populate them on application start to eliminate all manual work of maintaining the JSON. My thoughts on implementation would be to have an interface and create an implementation for MySQL where others could follow with additional implementations as required. The selection of the implementation would be done on application start and could have a predefined schema for RDBMS implementations.

What are your thoughts on this project? Are you all interested or have any special requirements?

I am willing to be the author for this issue.

Edit: clarity

Start by reviewing the /populate endpoint and the application-startup flow described in the issue. Define the persistence interface and MySQL implementation around saving proxies and toxics, with implementation selection at startup. Done means saved proxies and toxics are restored automatically after a server restart without maintaining a JSON array.