feat: add relation lookup column type

[Koc]

This is continuation of #2248 that allows to display more column from relation table.
There are 2 tables: employees and vacations. We can add vacation.requester relation column that referenced to the row id of the employee and display employee.name. But what if we need to display more column from the related table? e.g. employee.department. That's where relation lookup can help: select already existent relation and choose what extra column should be displayed.

🖼️ Screenshots

🗒️ TODO

• Merge Refactor: Extract getTableCellComponent helper for better reusability #2763 first

[enjeck]

Even with the screenshots, I'm not sure what we're adding and what the usecase is?

[Koc]

@enjeck I've updated description:

There are 2 tables: employees and vacations. We can add vacation.requester relation column that referenced to employee.name. But what if we need to display more column from the related table? e.g. employee.department. That's where relation lookup can help: select already existent relation and choose what extra column should be displayed.

[enjeck]

That's where relation lookup can help: select already existent relation and choose what extra column should be displayed.

Having a relation column, and a lookup column is extremely confusing. Even with this, I had to think extra hard to understand how they're different. If I'm struggling to understand as the dev, I doubts users will easily get it (or maybe it's just me, lol).

I would need others to check if they understand this just from the description and images. Maybe @nextcloud/designers need to weigh in

[Koc]

well, that's pretty similar to Excel's VLOOKUP function. But I'm open to changes here, let's wait for our designers

[kra-mo]

I certainly think the names should be changed at least. @marcoambrosini, ideas?

Let's also just say that Excel's ancient statistics-oriented DSL is maybe not the best language to draw inspiration from when it comes to design ;)

[marcoambrosini]

the "Lookup" term is used for this in both Baserow and Airtable. For the relational ones they use the wording "Link to table". I would do the same

Maybe this can help: https://baserow.io/user-docs/lookup-field

[Koc]

@samin-z I've rebased branch, fixed conflicts and code review comments, pipeline, added new tests.