Add expires_at option to ActiveStorage::Blob#signed_id

[aki77]

Motivation / Background

When using the expires_in option to generate an expiration URL, the URL will change each time.
By using the expires_at option as shown in the example below, the browser cache can be used for a certain period of time.

rails_blob_path(user.avatar, disposition: "attachment", expires_at: 2.hours.from_now.beginning_of_hour)
<%= image_tag rails_blob_path(user.avatar.variant(resize: "100x100"), expires_at: 2.hours.from_now.beginning_of_hour) %>

Detail

Add expires_at option to ActiveStorage::Blob#signed_id and URL helpers.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[aki77]

Thanks!