Allow UI base url to be customizable

[mrparkers]

Description

This change allows the user to pass a BASE_URL environment variable when running the docker container in order to add a URL prefix to the UI.

Motivation and Context

This change is needed if you need to run Swagger UI behind some reverse proxy that does path re-writes. This will enable you to add a URL prefix (such as /swagger) to the UI and all of the CSS and JS files it needs, allowing you to use the UI at a new path instead of the root directory.

How Has This Been Tested?

Build a local docker image from this branch:

docker build . --tag swagger-ui:latest

Run the container normally (without the new environment variable) to make sure it is backward compatible:

docker run -p 80:8080 -e SWAGGER_JSON=/swagger/schema.json -v $(pwd)/schema:/swagger swagger-ui:latest

Visiting http://localhost:80 confirms that it still works.

Run the container with a new base url:

docker run -p 80:8080 -e BASE_URL=/swagger -e SWAGGER_JSON=/swagger/schema.json -v $(pwd)/schema:/swagger swagger-ui:latest

Visit http://localhost:80/swagger to see that it still works with the new URL.

Types of changes

• No code changes (changes to documentation, CI, metadata, etc)
• Dependency changes (any modification to dependencies in package.json)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[mrparkers]

Replaces #3054

[shockey]

How does this behave when the container is run multiple times? I think it would nest the folder each time, i.e. /swagger then /swagger/swagger and so on.

[mrparkers]

The state of the container is reset when you kill it, so each time you run the container, this script runs against a fresh file system, with all of the UI files in /usr/share/nginx/html.

I verified this locally by running it multiple times with the same base url, and a few times with the url switched back and forth to something else. Each time it worked as expected.

[shockey]

Approved.

Thanks for the detail in your PR description, it was helpful 😄

[shockey]

Not sure why I didn't hit merge on Wednesday...

Anyway, thanks for the contribution @mrparkers!