tie alias creation to premium subscriptions

[brassy-endomorph]

fixes #645

• split utils.py into smaller modules to get rid of circular imports
• add ALIAS_MODE config
• gate number of aliases on ALIAS_MODE and/or premium status

[glenn-sorrentino]

Subscribed users get 100 aliases. Single-tenant is unlimited. Free is none.

[glenn-sorrentino]

Will leave comments while testing:

First - In the screenshot, I have not subscribed and have no aliases. the To: string in the user's inbox is only applicable if they have at least one alias.

[glenn-sorrentino]

Other than the comment above, the functionality on the front-end works well!

[glenn-sorrentino]

Noticing during the cancel subscription flow that the page isn't redirecting back to the premium page...

[brassy-endomorph]

subscription flow that the page isn't redirecting back to the premium page...

@micahflee you recognize this?

[glenn-sorrentino]

Also when I click "Cancel Now" I'm directed to the disable auto-renew page, but that's a different feature from canceling...

[brassy-endomorph]

Those sound like bugs for other tickets because they're not directly related to this PR and shoulnd't be addressed here. That will just make this ticket massive and more difficult to get merged. I can do that in a followup too, but it's not really relevant to the changeset I'm proposing.

[glenn-sorrentino]

Those sound like bugs for other tickets because they're not directly related to this PR and shoulnd't be addressed here. That will just make this ticket massive and more difficult to get merged. I can do that in a followup too, but it's not really relevant to the changeset I'm proposing.

By "those", which of the above do you mean?

[brassy-endomorph]

https://github.com/scidsg/hushline/pull/699#issuecomment-2420027144

and

https://github.com/scidsg/hushline/pull/699#issuecomment-2420019089

Canceling / disabling autorenew should be separate tickets