[Feature] Decorators for Application Authentication

[b1scuit-thi3f]

At the moment, if we want utilise separate authentication from the core jimi auth within a plugin (see package deployer as an example), we have to roll our own auth handling.

Describe the solution you'd like It would be good to have decorators that allow jimi to handle authentication for different applications. This would mean each application/plugin could use their own authentication if they so wished.