Per #ledgersmb conversation with metatrontech:
One may have a third-party app, with tens of fields in the table corresponding to LSMB customers. Question asked where to store these additional fields.
"Add another schema and create a database tables for the fields. Then these could be linked against customer.id for now, and when you upgrade they could be moved to entity_credit_account.id. You should reference the tables by the full path, i.e. schema_name.table_name."
This bug requests that this advice solving a very common problem be codified into a FAQ or HowTo, perhaps with a SQL script to create the schema and interschema relations according to best practices and name conventions, for the benefit those without extensive SQL knowledge.
The integrator could customize the SQL script with their particular custom fields in the additional schema.
Proliferation of this style of additional data storage of may lead to smoother and better-documented migration to 1.3 for customized datasets.