cubicweb #1863109 facet / bookmark search doesn't escape values [validation pending]

When I use facets, if the original rql query contains + characters such as in:

Any X, GROUP_CONCAT(XA + " " + XB) ...

they get unquoted in the bookmarked query and .. disappear:

Any X, GROUP_CONCAT(XA  " "  XB) ...

and the RQL becomes invalid

prioritynormal
typebug
done in3.14.3
load0.250
load left0.000
closed by<not specified>