end-to-end API testing

Overhaul environment configuration system

• Port the dotenv file to a real shell script. Shell scripts are more portable as they don't require the installation extra dependencies. They also have proper support for double and single quoting and better support for variable expansion, which is not the case for many dotenv implementations (I'm looking at you docker-compose)

• Rename many variables, adding the DEMO_ prefix. This is to make it more clear which variables are fixtures for demonstration purposes.

• Add a number of new new variables and corresponding templates. Mostly to allow us more customisation of the demonstration fixtures when bootstrapping

Start implementing end-to-end style API tests

• Start adding utility libraries for interacting with the various components in the stack. So far very incomplete. These will be expanded over time and may become the basis of a library for provisioning the system

• Start adding tests, using unittest from the python standard library. This framework was chosen because it has no external dependencies and is available out-the-box on any Python installation. We can move to something more feature-complete in the future if needed.

• This commit contains mostly basic health-checks and a few create/read data tests. These will be expanded over time