Add ability to alter foreign keys

[karatakis]

PR Info

• Closes Ability to alter foreign keys #184

Adds

• Ability to alter foreign keys on TableAlterStatement

Breaking Changes

• Change method signature prepare_foreign_key_create_statement_internal of ForeignKeyBuilder to include inside_table_single_alter: bool

Changes

• Add method prepare_foreign_key_drop_statement_internal in ForeignKeyBuilder

[ikrivosheev]

@karatakis Thanks for the PR. I left some comments)

[karatakis]

Thanks for the review @ikrivosheev. I will resolve them ASAP

[tyt2y3]

Thank you for the contribution. Just a question, isn't that we have ForeignKeyDropStatement already? So you want to drop multiple keys in one statement?
I think the API looks good. As mentioned by ikrivosheev, refactoring the code a bit would make it easier to maintain.
Thank you again!

[karatakis]

@tyt2y3 ForeignKeyDropStatement works just fine, but allows only single foreign key constrain modification. Yeah, the new code enable us to modify multiple foreign key constrains. I am open to any comments that will allow the project to be easier to maintain.

[ikrivosheev]

@karatakis thank you, some small comments.

[tyt2y3]

Would appreciate some tweaks

[ikrivosheev]

@karatakis thank you for contribution!

@tyt2y3 LGTM!