Add transactions queries

[katarinasupe]

Description

I added get transactions and terminate transactions methods for easier transaction management.

Pull request type

• [x] Feature

Related issues

Closes #240

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation TODO generate reference guide
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes

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Reviewer checklist (the reviewer checks this part)

• [ ] Core feature implementation
• [ ] Tests
• [ ] Code documentation
• [ ] Documentation on gqlalchemy/docs

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