Feat: agency logos configurable via Admin

[lalver1]

Part of #2489

This PR implements storing the agency logos as a property on the TransiAgency model. The logos are saved to the application's local filesystem.

Notes

Pending work (for a followup PR)

• Change the modal--agency-selector template to use the new png logos and ensure that the new png logos display correctly on the browser (initial testing shows that the aspect ratio is off)

The logo's file format

We expect the logo to be uploaded to be a .png file and smaller than 1MB (the default value of the client_max_body_size size nginx directive) due to the current nginx configuration. Otherwise, a 413 request entity too large error will be raised. If we expect larger files, we should explicitly set client_max_body_size size to a larger size in nginx.conf.

Updating a logo

Currently, an existing logo is not overwritten if a new logo is uploaded. Instead, the new logo has the same name as the old logo but with a random string appended to the end of it. Do we want this behavior or do we prefer to overwrite the files? If we prefer an overwrite, we may need to override save in FileSystemStorage. For the current iteration we will use this default behavior but in the future we will implement file management improvements.

Reviewing

Assuming we start from the main branch, with DJANGO_DB_DIR=., and from an exited dev container

1. Check out this branch locally, ensure you have no pending/unstaged changes (git status)
2. (outside of the dev container) docker compose build --no-cache client to rebuild the app image
3. Rebuild and reopen the dev container to confirm that the migrations ran ok and that the database has the new fields
4. Reopen folder locally in VSCode (stopping the dev container)
5. In .env set DJANGO_DB_DIR=/home/calitp/app/data
6. In compose.yml, set the volumes of the client service to - ./:/home/calitp/app/data (discard this change after this review)
7. (outside of the dev container) docker compose up -d client to start a new app container mimicking the location of the persistent storage in the deployments
8. Navigate to the app's admin panel using your browser and upload a png for a transit agency (you can use the same file for both the small and the large logo)
9. Using either Docker Desktop's Exec window (click on the app container and navigate to the Exec tab) or docker compose exec -ti client /bin/bash to connect to running container, confirm that the files (cst-sm.png and cst-lg.png, for example if the selected transit agency was CST) were created in /home/calitp/app/data/uploads/agencies

[github-actions]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
benefits
settings.py
benefits/core
models.py
Project Total

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