See https://www.drupal.org/project/drupal/issues/2986962

Import the file_url_generator 8.x-3.x changes into the 4.x branch.

@todo Change exception type.

Issue #3346165 by cmlara: stream_flush should not return TRUE if cache write fails due to file not existing

Issue #3342835 by cmlara:  Make waitUntilFileExists() and writeUriToCache() not public in S3fsBucketStream

Removing waitUntilFileExists() from S3fsImageStyleDownloadController without replacment as file existence
should be handled as part of S3BucketStream and S3fsFileSystemService.

Issue #3225789 by cmlara, jlscott: Invalid configuration value provided for "use_path_style_endpoint"

Issue #3223912 by cmlara, Darvanen: Outdated warning regarding upload all files as private and use_s3_for_public in settings form

Issue #3223654 by cmlara, yijiang, Darvanen: upload_as_private not respected for validate(), S3fsFileService, and  S3fsFileMigrationBatch

Issue #2976430 by gagsfitz@gmail.com, Manuel Garcia, cmlara, malcolm_p, jacobbell84, Darvanen, douggreen: Integrate with the key module for access and secret keys

Oleh Vehera authored Jul 05, 2021 and Conrad Lara committed Jul 05, 2021

Issue #3209162 by Simon Peacock, voleger, cmlara: Allow domain name to map directly to root path - D8

Issue #3134530 by davidlfg, cmlara: cURL error (60) SSL certificate problem: self signed certificate

Allow calls using the managed FileSystem service to directly call the AWS API
to avoid the StreamWrapper need to allocate a temp file and copy the content twice.

This maintains the ability to report when copy errors occur.

Correct docblocks and API documention.
Correct contructors not typehinting with interfaces.
Remove outdated todo's.

Issue #3219242 by cmlara: MimeTypeGuesser::guess() is deprecated in drupal:9.1.0 and is removed from drupal:10.0.0. Use ::guessMimeType() instead