Adding support for schemas

[Akamatsu21]

Hello, as per the discussion in this thread, myself and @tisauro have decided to make an attempt at implementing the schema support for cedar-agent. I have made a new branch for this which you can find in this repo. This is a rough plan I've been following with this:

• Create the SchemaMemoryStore with get, update and delete operations
• Implement creating schema from file
• Add API endpoints for the three operations
• Add validation to policy create/update endpoints
• Add validation to entity create/update endpoints
• Add validation of existing policies/entities to schema create/update endpoints
• Write unit tests
• Update documentation and examples

I've not created a pull request for now as the feature isn't finished yet (although I am happy to make one if it makes it easier to browse the changes?). I wanted to ask if one of the main contributors to this project would be able to spare some time and have a look through what I've done so far, to confirm that this is in line with your expectations and there aren't any glaring mistakes? I would consider myself intermediate at Rust, so I'd be very happy to learn if anything could have been done better.

[orweis]

Hi @Akamatsu21 - for sure @omer9564 will be able to review this once you have a PR, might take a little while to do so, but we can definitely make sure to cover it (CC: @obsd )

[Akamatsu21]

Hi @orweis and thank you for your reply. I have created a PR here with what I have for now. As the next step (validating entities) is looking a bit more complex than initially expected in terms of structuring it into the code, I figured I should have the branch in its current state reviewed first before I make more changes. Hope this is okay.

[omer9564]

@Akamatsu21 fixed it in the PR, it was merged and released as cedar-agent version 0.2.0 available both in crates.io & dockerhub

[Akamatsu21]

Thank you very much, feels good to see it all done now :)