Move models into ~/schema

[kulla]

After the refactoring we want to remove ~/model. There are some Models which should be easily migrateable into ~/schema:

• Move ai.ts into ~/schema #1594
• https://github.com/serlo/api.serlo.org/blob/staging/packages/server/src/model/google-spreadsheet-api.ts
• https://github.com/serlo/api.serlo.org/blob/staging/packages/server/src/model/kratos.ts
• https://github.com/serlo/api.serlo.org/blob/staging/packages/server/src/model/mailchimp.ts

[AndreasHuber]

I would prefer migrating https://github.com/serlo/api.serlo.org/blob/staging/packages/server/src/model/ai.ts directly into the frontend instead.

[kulla]

I would prefer migrating https://github.com/serlo/api.serlo.org/blob/staging/packages/server/src/model/ai.ts directly into the frontend instead.

I am with you that this is might be a good simplication. However the backend in the frontend does not know about kratos / our users. So checking whether the user has the rights to do the prompt is not easy to be done yet.