Fix allowed chars in mailer subject

[Denitz]

Pull Request for Issues #31768, #40571.

Summary of Changes

Currently, email subject is validated as email address, hence it's impossible to send an email with a subject like Test email for test@test.com {test}

The problem is that email subject is incorrectly validated as email address since 2006, see dec8927#diff-89c219c58287d02dd7de50360cf6656e7ab96bfd20ef065ef54db235ff12dea4R127

Current MailHelper::cleanSubject() was never used, we can use it.

Testing Instructions

Send an email with subject Test email for test@test.com {test}

Actual result BEFORE applying this Pull Request

See error

Expected result AFTER applying this Pull Request

No errors

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[TLWebdesign]

I have tested this item ✅ successfully on e8b28cf

Tested this using mass mailer function and send an e-mail. after patch mail was sent succesfully. before it did not send e-mail.

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[rachelwalraven]

I have tested this item ✅ successfully on e8b28cf

Jooma 4.3 dev with PHP 8.1

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[Magnytu2]

I have an error sending a message with or without special characters in the subject after applying the patch.

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[richard67]

I have an error sending a message with or without special characters in the subject after applying the patch.

@Magnytu2 This error seems not to be related to the changes in this PR. On which version of Joomla have you tested?

[richard67]

RTC

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[ChrisHoefliger]

I have tested this item ✅ successfully on e8b28cf

Tested on localhost Joomla 4.3.4 @pbf 2023

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[Magnytu2]

@richard67 test Joomla 5.0 Beta 1 - php 8.1.18 - 10.5.21 MariaDB.

[richard67]

@richard67 test Joomla 5.0 Beta 1 - php 8.1.18 - 10.5.21 MariaDB.

@Magnytu2 This pull request here is for the 4.3-dev branch, sou you cannot test it on a 5.0-beta1-dev.

[obuisard]

Thank you @Denitz for the PR!

[Denitz]

@obuisard Thank you!