Create an HTTP facade

[steve-r-west]

We will need to be able to make HTTP calls to services, so lets bootstrap something in the code. We can maybe copy the terraform provider one, and adapt, since it does a bunch of stuff already, like authenticating, etc...

https://github.com/elasticpath/terraform-provider-epcc/blob/main/external/sdk/epcc/auth.go
https://github.com/elasticpath/terraform-provider-epcc/blob/main/external/sdk/epcc/client.go
https://github.com/elasticpath/terraform-provider-epcc/blob/main/external/sdk/epcc/config.go

We will heavily refactor later, so don't bother linking to it.