feat: move most of auth handler logic to wuttjamaican

also deprecate the `rattail.db.auth` module

fix: rename some constraints per wutta model

we will not (yet?) be able to "inherit" from the wutta model Base
which means basically the two are "not related" at this point.

but we do want to *match* whatever wutta has defined so far. the
rattail auth tables may contain more columns but will at least include
those columns present for the wutta model.

part of matching is the constraint names, which have been manually
specified in rattail for a while now. finally wutta has bothered to
define a proper naming convention so we can simply omit the names for
future changes. however it also means we must add an explicit
migration for any models we must match to wutta, to abandon the names
we had previously set which are now "incorrect"

most constraint names can remain as-is i think, since most tables will
never exist in the wutta model. eventually might be good to rename
all at once but that can wait

fix: remove duplicate method for `AppHandler.load_object()`

that is now defined in wuttjamaican

fix: remove duplicate method for `RattailConfig.production()`

since it now is defined in `WuttaConfig`

feat: move some app model logic to wuttjamaican

previously the "canonical" way to get the model was via
config.get_model() - but now the canonical way is simply app.model

note that for now, even though wuttjamaican provides a default model,
the rattail model does not (yet?) inherit from it. also since
wuttjamaican does not yet support versioning, that feature remains in
rattail only for now.

various legacy things have been deprecated and will warn if used by
other apps.