Self service: allow to omit the agent version

[Al2Klimov]

• As discussed in Install no longer works because it can't find version 2.14.2 icinga-powershell-framework#795 (comment), pinning agent versions is a delayed shoot in the foot
  • Versions disappear from our IfW repo
  • Versions get CVEs
• As discussed in Install no longer works because it can't find version 2.14.2 icinga-powershell-framework#795 (comment), just using the latest agent (command endpoint only!!) version has never been a problem (if you don't count ancient SSL versions...)

So please make

icingaweb2-module-director/application/forms/SelfServiceSettingsForm.php

Lines 153 to 161 in de8fe10

	$this->addElement('text', 'agent_version', [
	'label' => $this->translate('Agent Version'),
	'description' => $this->translate(
	'In case the Icinga 2 Agent should be automatically installed,'
	. ' this has to be a string value like: 2.6.3'
	),
	'value' => $settings->getStoredOrDefaultValue('self-service/agent_version'),
	'required' => true,
	]);

optional and default to latest stable version.

CC @slalomsk8er

[LordHepipud]

Hello, why don't you just add "latest" to the version prompt in Director?

This will automatically install the latest version available in the repository.

[Al2Klimov]

The tooltip didn't tell this. I've figured out we can #2968 by stumbling over IfW code converting release/latest version to null.