pgsql: Add libpq connection parameter "scram_channel_binding"

Add libpq connection parameter "scram_channel_binding"

This parameter can be used to enforce the channel binding type used
during a SCRAM authentication.  This can be useful to check code paths
where an invalid channel binding type is used by a client and will be
even more useful to allow testing other channel binding types when they
are added.

The default value is tls-unique, which is what RFC 5802 specifies.
Clients can optionally specify an empty value, which has as effect to
not use channel binding and use SCRAM-SHA-256 as chosen SASL mechanism.

More tests for SCRAM and channel binding are added to the SSL test
suite.

Author: Author: Michael Paquier <michael.paquier@gmail.com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4bbf110d2fb4f74b9385bd5a521f824dfa5f15ec

Modified Files
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doc/src/sgml/libpq.sgml              | 24 ++++++++++++++++++++++++
src/interfaces/libpq/fe-auth-scram.c | 20 +++++++++++++++-----
src/interfaces/libpq/fe-auth.c       |  9 ++++++---
src/interfaces/libpq/fe-auth.h       |  1 +
src/interfaces/libpq/fe-connect.c    |  9 +++++++++
src/interfaces/libpq/libpq-int.h     |  1 +
src/test/ssl/t/002_scram.pl          | 14 +++++++++++++-
7 files changed, 69 insertions(+), 9 deletions(-)