Allow to set password_encryption algorithm

[op]

Description of changes:

This allow you to override the encryption algorithm used by the server when storing the password to support legacy clients like Redshift.

Redshift is not able to connect to PostgreSQL with scram-sha-256. This message is returned:

authentication method 10 not supported

Possibly Redshift is using an old version of libpq which only support md5. This change fixes the problem for us.

References:

• https://docs.aws.amazon.com/redshift/latest/dg/r_CREATE_EXTERNAL_SCHEMA.html

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