API conventions

API definition

POST /scope/object.action

Every endpoint HTTP method should be POST

For browser cache you can use GET as an exception:

GET /scope/object.action?arg=value&foo.bar=deep
scope is optional. It helps to group few methods by sense.
object.action - use only this order and only in camelCase
- if there are few objects - it makes sense to use format first/second.action
All params should be passed as JSON object in body of request. There no need to use additional wrapper for fields (data/params)
- Additional wrapper may be needed only for complex filters {where: { card: 1 }, fields: ['name', 'author']}

Response has only 3 possible statuses:
- 200 - for any success request (in business-logic context)
- 400 - for any failed or mistaken request
- 500 - for other crashes
[200] Success response should return JSON object. Even if there isn't any data then should be returned empty object

Every response entity should have own property:
- { user } - "one user"
- { users, cards } - "users and theirs cards"
[400] Failed response should return error as field code with enum value (in snake_case)
- Error code should describe situtaion explicitly (what and where problem was happened).
- Server can send field message with more details about error;
- Field error always should has true value
```
{
    "code": "already_saved", // "card_not_found", "no_access"
    "message": "Card has been already saved in user favorite collection",
    "error": true,
}
```
[500] Infrastructure error alwasys should be in 5XX errors.
- It may not have a body at all, or it may not have json
- Cannot be parsed
- Some requests that return 500 can be safely repeated once.
  - The server should not keep an invalid state on a 500 response (transactional)