throw exception if a copy_to is within a multi field
Copy to within multi field is ignored from 2.0 on, see #10802.
Instead of just ignoring it, we should throw an exception if this
is found in the mapping when a mapping is added. For already
existing indices we should at least log a warning.
We remove the copy_to in any case.
related to #14946
Until a couple of hours ago we expected the position_offset_gap to default
to 0 in 2.0 and 100 in 2.1. We decided it was worth backporting that new
default to 2.0. So now that its backported we need to teach 2.1 that 2.0
also defaults to 100.
Closes#7268
Britta Weber
Clinton Gormley
Sarwar Bhuiyan
Andreas Kohn
xuzha
Nik Everett