- We need to indicate when login comes from UI to make sure (in future) user accepted terms of use & privacy, not being logged in automatically.
- it helps make source field required (task), previously when the user was logging form UI source was undefined
As an alternative, we can use only sth like: LOG_IN_FROM_FORM and PlatformDetails to distinguish between web/native, but I think it's safer to rely only on one specific param.