validate the 'id' parameter format

* Must be a postgres-compatible UUID
* Does not have to be an IETF 4122 compatible UUID
validate id format
use POSIX character class for hexadecimal characters
use beginning/end of string matchers

(not beginning/end of line matchers)
fix rubocop violations
Revert "validate id format"

This reverts commit 8773ed659843ad282703fdfb5a410fc5cc77a88e.

We decided this doesn't pull its weight.
Merge pull request #17 from CruGlobal/uuid-validation

Uuid validation