Merge branch 'pw-remove-please-from-database' into 'master'

...evelopment/database/add_foreign_key_to_existing_column.md

doc/development/database/avoiding_downtime_in_migrations.md

doc/development/database/background_migrations.md

doc/development/database/database_reviewer_guidelines.md

doc/development/database/not_null_constraints.md

doc/development/database/rename_database_tables.md

doc/development/database/strings_and_the_text_data_type.md