feat: make ssr catalogue work on simplified data model M11067

[mswertz]

demo:

• user interface works mostly as it works now

acc:

• [ ] rewrite 'cohorts' screen to work with 'collections' table
• [ ] rerwite 'variables' screen tot work with new 'variables table'
• [ ] mappings for multiple repeats are shown as one mapping record in mapping details

[connoratrug]

where are the data and model ?