Completing Listing REST endpoints for GET all and POST

[Amormio25]

Describe your changes

• wrote code for getting all listings in db (GET all)
• wrote code for creating a new listing in db (POST)
• fixed requested changes and renamed branch for all work relating to listings

Issue ticket number and link

[ Insert Link & Ticket #]

Checklist before requesting a review

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• This change requires a documentation update

[arnavjk007]

We will also have it where only certain roles can create listings or ping these APIs. So just keep note or maybe comment as a reminder to implement user auth and permissions once that is implemented. For example, only lab admins can create or delete listings so we need to check permissions before we do the process.

[arnavjk007]

Some minor changes + sorting changes

[arnavjk007]

Restructuring change for consistency across all services

[arnavjk007]

Some minor changes

[arnavjk007]

This looks good, I think the final thing we need is a little bit of unit testing to make sure that the apis work properly. I set up jest on the main branch so make sure to do git merge main in your feat branch to get the updates. Unit testing goes into each folder and creates a new tests file with .test.ts.