What you are describing as code reuse exists for databases, but they are called applications and generally utilize a general purpose programming language. It doesn’t make sense to have a SLA data model library because every use case is different. It’s a database, not procedural code.
There's a reason monstrosities like SAP exists, they're practically what you describe.
If stuff like SAP is the future of Line Of Business (LOB) apps, instead of having a rich Open Source ecosystem of data storage and data access libraries, then we've lost.
What you are describing as code reuse exists for databases, but they are called applications and generally utilize a general purpose programming language. It doesn’t make sense to have a SLA data model library because every use case is different. It’s a database, not procedural code.