feat: public listing detail page supports external listings - #6525

This PR addresses #(6367)

• Addresses the issue in full
• Addresses only certain aspects of the issue

Description

For external listings ingested by the system, they need to be displayed on the listing details page. To do this, the system fetches the live data from the external system. If the listing has a common app, it will reroute the user to the external site to apply.

How Can This Be Tested/Reviewed?

With Bloomington: Run yarn setup
With Bridge Bay: Run yarn db:setup:staging-region

Sign in as an admin through the partners site or the api
Through the api, call the /externalListings/ingest endpoint with the relevant data (found below)
On the public site, navigate to the listings browse page
Click on a internal listing, confirm listing detail page loads as expected. Click Apply now and confirm start page loads
Return to the listings browse page
Click on a external listing, confirm listing detail page loads as expected. Click Apply now and confirm you are redirected and start page loads

Call the ingest endpoint with the following payload, using the desired jurisdiction id to associate the listings with:
{ "externalURL": "https://hba-0-3-alameda-staging.herokuapp.com/", "jurisdictionId": "{id}", "targetName": "San Jose" }

Author Checklist:

• Added QA notes to the issue with applicable URLs
• Reviewed in a desktop view
• Reviewed in a mobile view
• Reviewed considering accessibility
• Added tests covering the changes
• Made corresponding changes to the documentation
• Ran yarn generate:client and/or created a migration when required

Review Process:

• Read and understand the issue
• Ensure the author has added QA notes
• Review the code itself from a style point of view
• Pull the changes down locally and test that the acceptance criteria is met
• Either (1) explicitly ask a clarifying question, (2) request changes, or (3) approve the PR, even if there are very small remaining changes, if you don't need to re-review after the updates