Improve documentation for Flows users

Is your feature request related to a problem? Please describe.

When developing flows in Windmill, complex column data types (like "user and groups") are a problem, because it's not clear, how to correctly send the data to the API.

There should be a documentation of those data types.

Describe the solution you'd like

For example the type "users and groups" would need the following information:

{ id: <string>, type: <number>, displayName: <string> }

Types: 0 = user, 1 = group

Only id and type are required when creating or updating rows.

The field always contains an array of user/group representations.

Describe alternatives you've considered

Try and error. Should not the goal when offering a low code solution.

Additional context

No response

Start by locating the Flows documentation and the API guidance for complex column types, focusing on the “users and groups” field described in issue #1735. Done means documenting its array representation, the id and type fields, the displayName field, the user/group type values, and which fields are required for row creation or updates.