This migrates the SQL backend such that v2 endpoints containing up to 3
URL's (public, internal and admin) stored in 'extra' are split into
unique endpoints.
Because legacy "endpoints" (each having publicUrl, internalUrl and
adminUrl) are no longer conceptually identical to v3's "endpoints" (each
having an interface and a url), new ID's are assigned to each entity and
each API continues to operate using with independent sets of endpoint
ID's.
Endpoints created on the v3 API are not exposed on the v2 API.
Change-Id: I2ba59d55907313ae65e908585fc49be0c4ce899a