1.1.3

###Added

• RandomHex dialect-aware SqlDefault subclass for generating random hex strings across all backends.
• Meta.constraints support on models — named UniqueConstraint objects are now captured by the migration autodetector, enabling AddConstraint/RemoveConstraint generation via makemigrations. (#2108)
• MySQL schema editor: _alter_field override using MODIFY COLUMN for NULL/NOT NULL changes; backtick-quoted ALTER_FIELD_* templates.
• MSSQL schema editor: _alter_field override with ALTER COLUMN for nullability, named default constraint management via sys.default_constraints, bracket-quoted templates, and self-referencing FK CASCADE → NO ACTION downgrade.

Fixed

• MySQL migrations: ALTER COLUMN ... SET NOT NULL / DROP NOT NULL now correctly emits MODIFY COLUMN col type NOT NULL/NULL.
• MSSQL migrations: DELETE_CONSTRAINT_TEMPLATE and UNIQUE_CONSTRAINT_CREATE_TEMPLATE now use bracket quoting [name] instead of double quotes.
• MSSQL migrations: self-referencing foreign keys with CASCADE no longer fail with error 1785; automatically downgraded to NO ACTION.