feat: add relation column type

[Koc]

This PR introduces a basic relation type. It allows to connect few tables together. We will store row id as a column value and display selected column as a label for this values. Closes #172.

✔️ Implemented

🔍 Column create/edit

🔍 Row create/edit via popup/inline

🔍 Row display in table/view + handle relation row removal

🔍 Filter for view

🔍 Filter for rows

🔍 Import/Export

🚧 Pending (help welcomed):

• Behat tests
• Cypress tests?

❎ What is out of scope:

• Lookup columns to add an extra columns from the related table to the current one. It will be handled separately in upcoming PR.

[Aveyron-RetD]

So I have user tested and this looks good. 👍 Could not get it to work at first because I did not get that only text field were working. This will create maybe some confusion on first use. Not all tables do have this text field. Perhaps a comment with a small tooltip with a little (i) in the screenshot below to explain that you can only link that kind of data

For my mention of #2035 this is not a good fit.
I was hoping that this would solve the one-to-many expansion I have been dreaming about, but no :-( .

[Koc]

I was hoping that this would solve the one-to-many expansion I have been dreaming about, but no :-( .

@Aveyron-RetD yeah, I'm aware about that case. But you need to understand me as well: feature is really huge, we should start from something simple and improve it in upcoming iterations 🤝

I will add tooltip soon. Hope that we can merge it soon 🙏

[enjeck]

would be nice to have tests to avoid regressions in the future

[Koc]

@Aveyron-RetD here we go, without tooltip

[Koc]

hey @enjeck @blizzz!

I've added Behat tests, please check. Is that enough to merge PR?

[enjeck]

Thank you so much!