Use cached getDisplayName method

[miaulalala]

instead of the current slower $usermanager->get($user)->getDisplayName()

Fixes #33598

[tcitworld]

With @nickvergessen's suggestions

[tcitworld]

Needs a rebase after #33615

[miaulalala]

Needs a rebase after #33615

will be done when squashing the fixups

stale

[miaulalala]

The $senderName variable doesn't need a check on null as it's checked again later and it will use the $sender if the $senderName is null.

[tcitworld]

The $senderName variable doesn't need a check on null as it's checked again later and it will use the $sender if the $senderName is null.

But $sender is the email, not the uid. Also for the definition of $fromName it's not handled properly.

[miaulalala]

The $senderName variable doesn't need a check on null as it's checked again later and it will use the $sender if the $senderName is null.

But $sender is the email, not the uid. Also for the definition of $fromName it's not handled properly.

The fallback for not having a display name is the email, yes. Which is fine in this case, that is a good way to handle not having a Display Name for the sender when it comes to emails.

Added a null check on the $senderName for the $fromName, thanks for pointing that out.

[ChristophWurst]

Looks good