Weasyprint: Current and future kraft.* variables

[noseshimself]

the kraft.* variables permit to access to information about Kraft itself; they are mainly of interest for developers of (print) templates (e. g. to check for the presence of other variables that have been added at a certain kraft version).

Ideally this list will become the foundation of a paragraph in the Kraft manual.

[noseshimself]

kraft.* variables

The variables in this block contain the information about Kraft itself

current name	proposed name	description	comment
VERSION	version	Kraft version string, e. g. "Kraft 0.98+git Lyonel"
DB_SCHEME	db_scheme	Database version
SYS_USER	current_user	user name of the account generating the printout (but NOT necessarily the original document!)
HOSTNAME	hostname	the system name of the workplace generating this document
	datetime	current date and time
	db_type	currently MySQL or SQLite
	db_host	hostname/IP address and (:port) of the database server
	db_host_id	the connection identification string of the database server	(1)

1. The host ID string will help in case different types or versions of the same database engine are showing different results (this has already happened with mariadb)