[JENKINS-69032] Plugin manager update site URL can be saved empty

[benebsiny]

See JENKINS-69032.

Form validation and "Reset to default" button are implemented.

Proposed changelog entries

• Add a "Reset to default" button to reset update site url to default.

Proposed upgrade guidelines

N/A

Submitter checklist

• (If applicable) Jira issue is well described
• Changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developer, depending on the change) and are in the imperative mood. Examples
  • Fill-in the Proposed changelog entries section only if there are breaking changes or other changes which may require extra steps from users during the upgrade
• Appropriate autotests or explanation to why this change has no tests
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadoc, as appropriate.
• New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO") if applicable.
• For dependency updates: links to external changelogs and, if possible, full diffs

Desired reviewers

@mention

Maintainer checklist

Before the changes are marked as ready-for-merge:

• There are at least 2 approvals for the pull request and no outstanding requests for change
• Conversations in the pull request are over OR it is explicit that a reviewer does not block the change
• Changelog entries in the PR title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood
• Proper changelog labels are set so that the changelog can be generated automatically
• If the change needs additional upgrade steps from users, upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the PR title. (example)
• If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[NotMyFault]

Does the FormValidation validate the input though? It looks like you'd be able to hit the submission button still, even if the field is empty.

[benebsiny]

@NotMyFault The FormValidation can only shows the error message at most, just like some input fields in the Configure System page. In my opinion, if a user change the update site url to empty accidently, he/she can reset back easily by clicking the "Reset to default" button.

[daniel-beck]

Given that accepting user submissions even if they're nonsensical is a fairly common pattern in Jenkins, validation + reset button doesn't seem like a bad solution.

[daniel-beck]

It might also be useful to review the error that appears when you check for updates from an empty URL update site to make sure that explains the configuration is screwed up and should be changed. Not necessary if you don't feel like adding that though.

[jtnord]

Looks ok to me. Chinese translation passed the google translate check

[jtnord]

LGTM - left a few untested suggestions.

[jtnord]

should this also have a read timeout?

Suggested change

	conn.setConnectTimeout(5000);
	conn.setReadTimeout(1000);

[benebsiny]

Will 1 sec too short? How about 5 sec which is same as connect timeout?

[NotMyFault]

Thanks for addressing the outstanding concerns, looks promising so far.

[timja]

/label ready-for-merge

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This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

Thanks!

[jtnord]

caused https://issues.jenkins.io/browse/JENKINS-70240