Rename `$this` when used in `@param` tags

[espellcaste]

Inspired by ​https://core.trac.wordpress.org/ticket/52243 and confirmed we have many instances of the same. The description below is basically copied and pasted from that ticket.

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Several filters and actions pass $this as a parameter. $this is a pseudo-variable that cannot be used as the name of a function parameter.

I've identified a few problems caused by using $this as the name of a parameter for actions and filters:

• Inexperienced developers may copy and paste the list of parameters from the apply_filters() call or from the ​https://developer.buddypress.org site when adding their filter and then experience a fatal error
• Developer tools that consume filter and action docblocks, for example code generators, have to rename $this to avoid the same
• PHPStan and other static analysis tools report $this as invalid when used in a @param tag

Usage of $this in @param tags for actions and filters should be replaced with a more appropriate variable name.

[devutpol]

Replace usage of $this in action and filter parameter docblocks.

[espellcaste]

This looks good! @imath could you also review this patch and confirm the arguments name are okay to you?

[imath]

Thanks for the ping @espellcaste and thanks for the patch @devutpol. I quickly had a look about it. But I'll need some more time because I've found something inconsistent at first sight in src/bp-core/classes/class-bp-email-recipient.php $recipient being used for BP_Email_Recipient and BP_Email, BP_Email is more representing a full email object with subject, content, sender and recipient.

[espellcaste]

@imath Any feedback?

[imath]

In 13372:

Replace usage of $this in @param tags with a meaningful variable name

Props devutpol, espellcaste

Fixes #8611

[imath]

In 13421:

Add missing backticks in @since docblock

This commit is mainly an attempt to make sure a contributor rightly gets a
BuddyPress badge on his WordPress profile page.

Props devutpol

See #8611

[espellcaste]

Related #9164