Merge pull request MongoEngine#2740 from bagerard/prepare_0_27

Prepare 0.27

Merge pull request MongoEngine#2727 from bagerard/prepare_0_26_0_release

prepare_0_26_0_release

Merge pull request MongoEngine#2718 from bagerard/prepare_release_0_25_0

improvements for 0 25 0

Merge pull request MongoEngine#2676 from bagerard/prepare_0_24_2

prepare_0_24_2

Merge pull request MongoEngine#2637 from bagerard/prepare_0_24_1

Prepare release 0 24 1

Merge pull request MongoEngine#2623 from bagerard/prepare_release_0_24_0

Prepare release 0 24 0

Merge pull request MongoEngine#2513 from bagerard/prepare_release

Prepare release

Merge pull request MongoEngine#2487 from bagerard/prepare_0_23_0

update changelog for 0.23.0 release

Merge pull request MongoEngine#2453 from bagerard/prepare_0_22_1

Update changelog for 0.22.1

Merge pull request MongoEngine#2447 from bagerard/_changelog_0_22_0

prepare 0.22.0