feat: allow `buildUrl` to use pre-encoded URLs

[heyitsbryanm]

Describe the feature

If the buildUrl function builds a Web Proxy URL with a pre-encoded URL, the URL will be double encoded. This returns a 400 error in the Rendering API.

To Reproduce

1. Create a Web Proxy Source in imgix
2. Use this Swift code (use your own secureUrlToken):

let signedClient = ImgixClient.init(
  host: "imgix-web-proxy-test-source.imgix.net",
  secureUrlToken: "EHFQXiZhxP4wA2c4"
)

// This will return a `400` error
signedClient.buildUrl("http%3A%2F%2Fassets.imgix.net%2Fexamples%2Fcat.jpg") // => https://imgix-library-secure-test-source.imgix.net/http%253A%252F%252Fassets.imgix.net%252Fexamples%252Fcat.jpg?s=5751ef13a5ca325fab9c4038b080cd80

[luqven]

Hey @heyitsbryanm, thanks for opening this issue!

This library expects you to give buildUrl() un-encoded paths.

In order to support encoded paths, we'd need to support a flag to remove all URL encoding (which means the URL might not get formatted in a way our render stack can parse) or support the end user passing us a custom encoding function, to replace our encoding behind the scenes.

I can't give you an exact time estimate, but I will now mark this as a feature request and add it to our backlog.

If someone else is interested in this feature, comment or react to this issue to help us prioritize.

[heyitsbryanm]

Gotcha - changing the description to feature request 👍.