Switch database name when appropriate on session override.

[ close #2714 ]
[ close #2718 ]
Fix find_or_(create|initialize)_by on scoped relations.

[ fix #2707 ]
Update license dates
Cache exists and first when appropriate.

[ close #2667 ]
Make #distinct available at the class level.

[ fix #2719 ]
Allow index definitions on specific databases.

[ close #2615 ]
Allow passing a block to instantiate
Only validate changed associated documents. (regression)

[ fix #2703 ]
Update changelog
Update changelog
Update changelog
Update changelog to reflect #2683 pullback
Update changelog to reflect #2671 pullback
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Ensure that .sort method change criteria

.sort method was not changing the criteria, so when .first applied it assumed there was no sort and it was ignoring it
making apply_sorting a block function to unsure it will reset the query after execution of .first or .last
Update changelog
Revert #2703
Update CHANGELOG.md

"Resolved Issues" title moved on top of resolved issues list in 3.0.18 changelog
Support int keys when using dot notation on read.

[ fix #2740 ]
Update changelog