Investigate axios timeout limits

[christroutner]

It has been brought up that one of the reasons why rest might have scaling issues is because axios does not quit in a timely manner if a downstream service rest is trying to talk to does not return. The scope of this Issue is to investigate axios limitation with timeout and if there is a need to manually specify a timeout value.

[christroutner]

Article on setting timeouts in axios:
https://medium.com/@masnun/handling-timeout-in-axios-479269d83c68

[paOol]

PR here - #549

The default BCH related endpoints were set to 15 seconds, and SLP related are 30 seconds.

a 500 response is sent in the event that the call exceeds the timeout.

axios.all() was replaced with Promise.all() because the all() method is only accessible to the main axios object and not new instances of axios. Also because they do the same thing.

all tests were passing.

[christroutner]

I created this repository to explore the axios timeout settings and how to mock unit tests for that timeout behavior:
https://github.com/christroutner/axios-timeout-test

Unit tests need to be incorporated into the code changes in PR #549

[christroutner]

PR #549 was replaced with PR #550