Implement basic integration tests and continuous integration

[marcosfelt]

Set up Github actions and use pytest mock to mock _resilient_request and add units tests for the following services.

• Github actions Add Github Actions #8
• OPSIN Testing infrastructure #5
• OPSIN batchmode Test opsin batchmode #11
• Pubchem
• CompTox
• CTS
• Chemeo
• CAS
• CIR
• NIST
• CHEBI

I need to note down for each service which examples are failing and add a json field with services that are expected to fail. Then, I could check if the behavior is doing what we want. Going to do the unit tests in a separate issue.

[simonmb]

To mock the request maybe the best would be to run the moleculeresolver on a set of molecules and save the status code and the content of the request let's say for example to a json file used in the mock? Do you need a list of identifiers/modes to do this?

[marcosfelt]

That's a good idea - maybe we could have a script that does this. Would you be able to write that?

[simonmb]

Yes I'll send you a json with identifiers and modes via email.

[simonmb]

@marcosfelt, would you have some time to look at this? I edited your list and checked the services references in the PR I just merged. However I believe the test are not running for all services as there is a portion of code commented.