* Add `__eq__` method for `Index`instances
* tests: add Index test case
* refactor: compare index instances before set hash and eq func to class
* fix: sort fields when generating index hash
* docs: update changlog
* fix style issue
* refactor: use CustomIndex instead of postgres special HashIndex
* Check tortoise version before patch Index
* Add comment
* Add comment for why > work
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Co-authored-by: dbf <somnium@riseup.net>
