pgsql: Add header matching mode to COPY FROM

Add header matching mode to COPY FROM

COPY FROM supports the HEADER option to silently discard the header
line from a CSV or text file. It is possible to load by mistake a
file that matches the expected format, for example, if two text
columns have been swapped, resulting in garbage in the database.

This adds a new option value HEADER MATCH that checks the column names
in the header line against the actual column names and errors out if
they do not match.

Author: Rémi Lapeyre <remi(dot)lapeyre(at)lenstra(dot)fr>
Reviewed-by: Daniel Verite <daniel(at)manitou-mail(dot)org>
Reviewed-by: Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/CAF1-J-0PtCWMeLtswwGV2M70U26n4g33gpe1rcKQqe6wVQDrFA(at)mail(dot)gmail(dot)com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/072132f04e55c1c3b0f1a582318da78de7334379

Modified Files
--------------
contrib/file_fdw/expected/file_fdw.out | 19 ++++++++++-
contrib/file_fdw/sql/file_fdw.sql | 9 +++++
doc/src/sgml/ref/copy.sgml | 8 +++--
src/backend/commands/copy.c | 60 +++++++++++++++++++++++++++++++++-
src/backend/commands/copyfromparse.c | 53 ++++++++++++++++++++++++++++--
src/include/commands/copy.h | 13 +++++++-
src/test/regress/expected/copy.out | 23 +++++++++++++
src/test/regress/sql/copy.sql | 33 +++++++++++++++++++
8 files changed, 210 insertions(+), 8 deletions(-)