Add synthesize_regexp, a transform that reads values with regular expressions
Add synthesize_regexp, a transform that reads values with regular expressions

The "synthesize" transform can only create new values by pasting entire old
values together. Create a new transform, "synthesize_regexp", that reads
pieces of old values with regular expressions and creates new values by
pasting these pieces together, using named captures to select pieces.

Example:

- net.ip.prefixlen:
    synthesize_regexp:
      sources:
        ip_network:
          key: "pallet.ip_network"
          regexp: "_(?<prefix_length>[0-9]+)$"
      produce: "#[prefix_length]"

creideiki/palletjack,creideiki/palletjack,saab-simc-admin/palletjack,notCalle/palletjack,notCalle/palletjack,saab-simc-admin/palletjack