Restrict names in schema to lower_snake_case (breaking change)

[domire8]

As a small note, our application schema restricts most namespaces to the regexp (^[a-zA-Z][a-zA-Z0-9_]*[a-zA-Z0-9]$)|(^[a-zA-Z]$), so it does not actually enforce lower case for things like named service calls in the YAML. Changing it to (^[a-z][a-z0-9_]*[a-z0-9]$)|(^[a-z]$) would be nice but would be a breaking change to the schema unfortunately (potentially invalidates previously valid schemas).

Still, we should suggest lower_snake_case in the docs and automatically sanitize to lower case in the implementation, and update the schema when the next breaking change happens.

Originally posted by @eeberhard in aica-technology/modulo#66 (comment)