You can model business hours and SLAs with relationships. Join on time and team.
SELECT support_request.request_time + team.response_sla AS respond_by_time
FROM support_request
JOIN team_sla
ON support_request.assigned_team = team_sla.team_id
AND DATE_PART('day', support_request.request_time) = team_sla.day_of_week
AND DATE_PART('hour', support_request.request_time) BETWEEN team_sla.start_hour AND team_sla.end_hour;
It's quite impressive how you've missed the core of my message.
Now bundle up your proposal, put it up on Github, license it as MIT, and publish it available on sqlpm.org (SQL Package Manager) so that I can re-use it.
What's that you say? I can't? There's no sqlpm.org? Not even a postgresqlpm.org?
Where's the SQL ecosystem?
Oh, wait, there isn't any because SQL is not really reusable. It's <<all>> one-off scripts, like back in the Dark Ages of software development.
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.
You can model business hours and SLAs with relationships. Join on time and team.