Split out 'domain' and 'api path' as configuration options from 'endpoint'

Problem/Motivation

In certain Azure configurations, the domain part of the endpoint is considered a secret, but the actual 'path' bit is generally the same across Azure setups.

Given that, it would be nice if instead of simply endpoint in the configuration, there were 2 separate config keys: domain and api_path.

This setup would allow committing the api path to the code repository, but keeping the domain separate (eg, either using the Key module to fill it out, or the settings.php approach.

Proposed resolution

• Split out the values
• Write an update hook to update existing configs
• Update code to concatenate these two values into the endpoint

Remaining tasks

User interface changes

API changes

Data model changes

The current endpoint value would be split into domain and api_path.