Generate file structures on dynamic loop

[yajo]

Just: {% yield single_var from looped_var %}{{ single_var }}{% endyield %}

The implementation could be similar to https://github.com/orgs/copier-org/discussions/908#discussioncomment-6505536:

Does single_var exist in context?

• yes: do nothing special
• no: raise YieldException("single_var", looped_var)

OK, we got the exception. Now, are you rendering a filename?

• Yes: start loop. Inject single_var in the context and keep rendering the contents (of the dir/file, recursively).
• No: just let the exception raise and print a nice message "Using yield outside of file names isn't supported".

Originally posted by @yajo in https://github.com/copier-org/copier/discussions/908#discussioncomment-6543747

[0xsoydev]

Hello there @yajo, I am new to the open source community, I would like to try and solve this issue, if you may, could you please assign this issue to me?