Better Postgres collation support check

[lizconlan]

Adds a check to for whether the current database encoding is compatible with the requested named collation when asking whether it is available for use.

Closes #3683

[coveralls]

Coverage decreased (-0.009%) to 92.967% when pulling 1d8f2a9 on 3683-postgres-collations into 857ee1c on develop.

[coveralls]

Coverage decreased (-0.009%) to 92.967% when pulling 15537e2 on 3683-postgres-collations into 857ee1c on develop.

[garethrees]

Looks good – great find!

I've pushed a couple of super minor fixups just for neatness.

Main thing was just making filter_collations a little clearer by explicitly passing the same arguments as the intended SQL.

[garethrees]

Also, changelog plz! 👍

[lizconlan]

Main thing was just making filter_collations a little clearer by explicitly passing the same arguments as the intended SQL.

Cheers, wasn't entirely happy with that tbh 👍

[coveralls]

Coverage increased (+0.03%) to 93.002% when pulling 0d8ab80 on 3683-postgres-collations into 857ee1c on develop.

[coveralls]

Coverage increased (+0.01%) to 92.97% when pulling d405806 on 3683-postgres-collations into 72c7d47 on develop.

[coveralls]

Coverage increased (+0.01%) to 92.97% when pulling d405806 on 3683-postgres-collations into 72c7d47 on develop.

[coveralls]

Coverage increased (+0.02%) to 92.98% when pulling d405806 on 3683-postgres-collations into 72c7d47 on develop.

[coveralls]

Coverage increased (+0.01%) to 92.97% when pulling 081f434 on 3683-postgres-collations into 72c7d47 on develop.

[lizconlan]

merged as hotfix/0.26.0.9 and hotfix/0.27.0.4