Support additional HTTP headers from Alexa to Baby Buddy server

[btoconnor]

My Baby Buddy instance is protected by Cloudflare Zero Trust. In order for the Alexa command to reach the baby buddy server, I need to specify Cloudflare Service Token headers in the request from the Alexa skill in order to bypass the login screen.

I have this working totally fine in a relatively straightforward patch, but it is specific to the Cloudflare headers. I'd be happy to clean this up and submit a PR as-is and just have support for Cloudflare, but I'd also be open to a discussion about how to specify this a little more generically (if easy enough).

Thoughts?

I can provide a quick gist too which shows the scope of the changes (it's fairly minimal).

[cdubz]

May as well make a PR. Even if we don’t merge as-is it can inform a discussion around what changes could make sense.

[cdubz]

I'm going to leave this open as-is based on the last two comments in #8 -- i.e., we want a more general solution to this.