Improve type-safety: manually generate TS types based OpenAPI schema

[brojd]

Problem

Currently in the frontend codebase most HTTP requests and responses are not typed. Any request payload can be passed when making HTTP call and then the response has any type which means that later developer doesn't have any restriction on how to use the data that's coming from the backend. This is error-prone and leads to type errors in the browser + bugs related to incorrect usage of API.

Ideally we should have a way of declaring TypeScript types based on Python models (we can probably use the approach of generating TypeScript types from OpenAPI schemas with tools like openapi-typescript or modelina ). The final result would be that if API contract changes and it affects / breaks frontend, we will know it during development, not after deployment.

There are several steps to achieve the final result:
1) Have a way to generate TypeScript types based on Python models and saving it within grafana-plugin directory
2) Use generated types on the frontend so that any HTTP request and response is correctly typed (#3331)
3) Automate generation of types (e.g. on prepush Git hook or similar). This way if changes in API breaks frontend, frontend build will automatically fail preventing us from introducing the bug (#3332)

This issue is about step 1)

Acceptance criteria

• developer is able to manually generate / regenerate TypeScript types based on Python models
• newly generated types are saved within grafana-plugin directory

Outcome

• better type-safety in code
• being able to catch type errors during development before they reach prod (shift left)
• better developer experience thanks to increased number of type declarations and improved intellisense

[github-actions]

The current version of Grafana OnCall, at the time this issue was opened, is v1.3.57. If your issue pertains to an older version of Grafana OnCall, please be sure to list it in the PR description. Thank you 😄!