feature: Easy associations between tenanted and untenanted models

[flavorjones]

(This is probably an advanced feature that does not need to make it into 1.0. I'm just trying to start a conversation and/or nerd snipe people into helping!)

I would like this gem to enhance active record associations to detect if they're between a tenanted model and an untenanted model, and in that case do the extra work to make sure the tenant is respected.

Example: I'm currently building some associations between tenanted and untenanted models. Here's the code I want to be able to write:

class User < TenantedRecord
  has_one :membership
end

class Membership < UntenantedRecord
  belongs_to :user
  belongs_to :account # this is also an untenanted model
end

and what I want to be able to do is automatically make sure that those associations have the correct scope to be able to retrieve the record in the other database. For example, the manual equivalent of the has_one might be something like:

class User < TenantedRecord
  # add a scope to make sure we only get the Memberships that match the User's tenant
  has_one :membership, ->(user) { where(tenant_id: user.tenant) }
end

and the belongs_to has to look something like:

def user
  User.with_tenant(tenant_id) { User.find_by(id: user_id) }
end

but I would prefer to raise a WrongTenantError if the call is in the wrong tenant context.

Some defaults could be assumed, for example the tenant would be determined on the untenanted table by a column named tenant_id, which could be overridden with an argument to the association.

[flavorjones]

Side note: we need to make sure this works well with fixtures as well. It needs to be a real association so that fixtures can resolve attributes like user: one, but also when the fixtures are loaded it should write the current/test-default tenant to the tenant_id column.

[miguelmarcondesf]

Hey @flavorjones
I started working on this issue and created a PR in draft for now so we can better discuss whether I'm on the right path
Thanks!