fix accessing deprecated Mail Message properties (#42)

* fix accessing deprecated property

* fix accessing deprecated property

fix getLink requiring params for links without arguments (delete-all)

composer: update master branch alias to 2.6-dev

switch do github actions

MailPanel: attachmentId cast to int

tests: change temp path

tests: fix random failure when messageId contained only digits

composer: change branch alias to 2.4-dev

composer: change branch alias to 2.4-dev

MailPanel: changed $mailer typehint in constructor to IMailer

[closes #18]