feat: virtual child doctypes

[alias]

allow virtual child tables by looking up child doctypes controller class an call its get_list

It is actually a small change that FMO dramatically increases the usefulness of virtual doctypes, which can now be child tables too.
I came across two small design issues (not really related to this)

• The handover of the parent into the get_list method (or any other child table controller method) is useful, as the (static) child controller has otherwise no way to figure out its parent (without risking a loop).
• the (boiler plate) virtual child table controller has all methods of a regular controller, - all of them are not used for a child table, so perhaps the boilerplate can be shrinked in case of child doc types to just that get_list(parent).

[git-avc]

💜

[ankush]

This alone wont support virtual child tables.

Firstly, there are following use cases:

1. Attaching a virtual child table virtual doctype.
2. Attaching a virtual child table to normal doctype.
3. Attaching same child table to multiple doctypes.

For all three cases, we should be able to do at least basic CRUD:

1. Create new rows on existing or new parent documents.
2. Read rows when parent is read. (only this seems to be achieved)
3. Update individual row.
4. Delete individual rows.

If you can achieve this in PR then we can proceed. Else merging just partial implementation is no good. Just reading can be achieved by copying these 3-4 lines of code to relevant doctype controller too.

[alias]

" Just reading can be achieved by copying these 3-4 lines of code to relevant doctype controller too."

Thats true, Thank you