Fix large _.template memory consumption

[slickmb]

Problem: In order to support accepting a function for options.msg, express-winston is calling _.template for every request. This compiles a brand new lodash template every request. Under heavy load, this has significant performance and memory usage implications.

Solution: During initialization, make the decision on whether to use a single cached template or a dynamic function that compiles a template for each request. This way, we get the efficiency of a precompiled template for the more common use cases, while remaining backwards compatible with published features.

In a future version, it might be worth considering dropping support for mustache formatting and just have express-winston consumers always provide a function if they want a custom options.msg. The api consumer can use JS template literals if they need templating in their custom message.

[bithavoc]

❤️ Would you like to add yourself to AUTHORS?

[slickmb]

Sure! Thanks!

[bithavoc]

Sick, thanks

[bithavoc]

@slickmb Released in express-winston@3.1.0