[services] Add attachment delimiter
Summary:
Depends on D4075
Adding an attachment holders delimiter. Holders are built from:
- hashes - these are hexadecimal values - 0 to 9 and A to F (or lower case)
- uuid - also hexadecimal - 0 to 9 and A to F (or lower case)
- ID_SEPARATOR - :
So it's impossible to have ; character that would not be a delimiter.
Test Plan: Services still build
Reviewers: palys-swm
Reviewed By: palys-swm
Subscribers: ashoat, palys-swm, Adrian, atul, yayabosh
Differential Revision: https://phabricator.ashoat.com/D4076