Feat: add all languages endpoint and test

[abdullai-t]

Summary / Highlights

This pull request introduces a new endpoint to fetch all languages and includes corresponding integration tests to ensure the functionality works as expected.

Details (Give details about what this PR accomplishes, include any screenshots etc)

Testing Steps (Provide details on how your changes can be tested)

Requirements (place an x in each [ ])

• [x] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x] I've tested my changes manually.
• [x] I've added unit tests to my PR.

Transparency (Project board)

• [x] I've given my PR a meaningful title.
• [x] I linked this PR to the relevant issue.
• [ ] I moved the linked issue from the "Sprint backlog" to "In progress" when I started this.
• [ ] I moved the linked issue to "QA Verification" now that it is ready to merge.