Support for specifying operator class in expression indexes (e.g. gist_trgm_ops)

[plusls]

Motivation

Currently, sea-query cannot generate index creation statements that specify operator classes for expression indexes, such as creating a GiST index with gist_trgm_ops on a column or expression. This limits usage of PostgreSQL features like trigram indexes on expressions.

Proposed Solutions

Add support for specifying operator classes on columns and expressions in index definitions, allowing statements like:

CREATE INDEX idx_email_trgm ON users USING GIST (email gist_trgm_ops);

or expression indexes with operator classes.

Additional Information