Implement get_property_from_related_entities

## Objective
Support progress toward the [Deploy...endpoint QA pipeline...][1] by _making a function to **reduce code repetition** (DRY principle) and **simplify** queries such as `select fieldName, someField from Entity join Entity_has_RelatedEntity`_

## Key Result
Commit _code for the `get_property_from_related_entities_

## Details

**Describe alternatives you've considered**
We could write functions like `get_professor_details` instead, because we have a finite number of _entities_ such that we could enumerate them in one file, and any repeated code could be refactored in the future. It’s almost too complicated and not conducive to an MVP to overly generalize our code before we even write simple examples of said code.

Through the process of writing this GitHub issue, I’ve convinced myself that this issue should not be worked on until after MVP v1.0 is shipped.

[1]: https://github.com/calpoly-csai/api/milestones