graph-api: added more validation

[aramikm]

Problem

Adds extra validation on graph-api dtos and request/path params

Closes #496

Discussion

• Since we are going to overhaul our way of e2e testing it didn't make sense to add tests which would be replaced in the future.

Steps to Verify:

1. Run the api
2. Go to swagger
3. Try some invalid values in requests

[saraswatpuneet]

These are good to know 💡

[saraswatpuneet]

👍🏽

[mattheworris]

• Read through the code
• Looks good, agree with other comments

🚢 it

[JoeCap08055]

Regarding e2e tests: if we have a working e2e test framework, then it's worth while to add tests, because the test scenarios themselves for endpoint validation won't change--only the test framework setup will change, and we'll add additional tests for worker scenarios.

But if you want to add tests in a separate PR, that's fine.

[aramikm]

I think it would makes sense to add those tests when the framework is ready simply due to improved velocity of writing and verifying them compared to current state that if something goes wrong I would have to dig to see if my written test is the issue or the framework setup.