Snake casing WORD regex mistakingly splitting lowercase mixed-digit field names

[michael-sayapin]

Proto file:

message BadRegexTestMessage {
  uint64 ds18b20_serial_code = 1;
}

Result:

class BadRegexTestMessage(betterproto.Message):
    ds18_b20_serial_code: int = betterproto.uint64_field(1)

ds18b20 becomes ds18_b20.

[michael-sayapin]

A proposed fix would be changing WORD = "[A-Z]*[a-z]*[0-9]*" for WORD = "[A-Z]*[a-z0-9]*".