Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

Summary

After PR #7237, the CloudFront URL signer has stopped URL-encoding spaces in S3 object keys, causing a breaking change in signed URL generation.

Background

Prior to PR #7237, when signing CloudFront URLs for S3 objects containing spaces in their keys (e.g., "My File.pdf"), the signer would automatically URL-encode the space as %20, producing a valid signed URL like https://example.cloudfront.net/My%20File.pdf?....

Current Behavior

After PR #7237, the CloudFront signer returns unencoded spaces in the URL (e.g., https://example.cloudfront.net/My File.pdf?...), which produces invalid URLs that fail in browsers and HTTP clients.

Expected Behavior

The CloudFront signer should either:

1. Automatically URL-encode special characters (including spaces) in object keys, OR
2. Clearly document that clients must URL-encode keys before passing them to the signer

Impact

This is a breaking change that affects:

• Existing applications relying on automatic URL encoding
• S3 objects with spaces or special characters in their keys
• Any workflow where user-provided filenames are used as S3 keys

Steps to ### Reproduce

// Example code demonstrating the issue
const signer = new CloudFrontUrlSigner(/* config */);
const url = signer.getSignedUrl({
  url: 'https://example.cloudfront.net/My File.pdf',
  // ... other params
});
console.log(url); // Contains unencoded space

Environment

AWS SDK version: [post-PR #7237]
Node.js version: [v22]

Proposed Solution

Either revert the behavior to automatically URL-encode keys, or update the documentation to explicitly state that URL encoding is the caller's responsibility.

Regression Issue

• Select this option if this issue appears to be a regression.

SDK version number

@aws-sdk/cloudfront-signer@3.946.0

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

v22.15.0

Reproduction Steps

// Example code demonstrating the issue
const signer = new CloudFrontUrlSigner(/* config */);
const url = signer.getSignedUrl({
  url: 'https://example.cloudfront.net/My File.pdf',
  // ... other params
});
console.log(url); // Contains unencoded space

Observed Behavior

https://example.cloudfront.net/My File.pdf?...

Expected Behavior

https://example.cloudfront.net/My%20File.pdf?....

Possible Solution

Either revert the behavior to automatically URL-encode keys, or update the documentation to explicitly state that URL encoding is the caller's responsibility.

Additional Information/Context

No response