GTUBE-like test patterns

Unlike SpamAssassin where GTUBE carries a spam score, in Rspamd it triggers an action and inserts the GTUBE symbol.

pattern	action	enabled
XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X	reject	Yes
YJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X	add header	No
ZJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X	rewrite subject	No
AJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X	no action	No

Because non-reject GTUBE-like patterns can be used to bypass spam filtering they are disabled by default; they can be enabled by setting gtube_patterns = "all" in local.d/options.inc (since version 3.8) or enable_test_patterns = true in older versions (2.3+).

Enabling non-reject GTUBE-like patterns is NOT recommended for production usage!

To disable GTUBE such that the reject pattern wouldn't be applied, set gtube_patterns = "disable".