Update PHP coding standards to avoid using self

[GuySartorelli]

We had a bug which it turned out was caused by an unexpected interaction between self and late static binding (see this PR).
This was raised in php-src where the response was that it was working as intended.

Going forward we should avoid calling static methods from self to avoid this class of bug.

Notes

• In refinement we decided it's easiest to just avoid using self altogether, rather than only avoiding it for calling methods

Acceptance Criteria

• The PHP coding standards are updated to explicitly disallow using self (e.g. self::get())
• The docs mention the rationale, i.e. we're avoiding a specific class of bug that is introduced when using late static binding downstream from self
• static is fine, because it explicitly uses late static binding anyway
• References to self in our codebase are updated to use the actual class that is intended to received the call.
• Update code-writing script and re-run to use self::class::myMethod() in traits

Code writing script

• https://github.com/emteknetnz/self-remover

Kitchen sink CI

• https://github.com/emteknetnz/recipe-kitchen-sink/actions/runs/9514611296

PRs

• DOC Do not use self #528
• ENH Use class name instead of self bringyourownideas/silverstripe-composer-update-checker#90
• ENH Use class name instead of self cwp-agencyextensions#123
• ENH Use class name instead of self cwp#337
• ENH Use class name instead of self cwp-core#131
• ENH Use class name instead of self silverstripe-elemental#1201
• ENH Use class name instead of self silverstripe-admin#1773
• ENH Use class name instead of self silverstripe-asset-admin#1467
• ENH Use class name instead of self silverstripe-assets#614
• ENH Use class name instead of self silverstripe-behat-extension#274
• ENH Use class name instead of self silverstripe-blog#761
• ENH Use class name instead of self silverstripe-cms#2955
• ENH Use class name instead of self silverstripe-config#115
• ENH Use class name instead of self silverstripe-contentreview#237
• ENH Use class name instead of self silverstripe-crontask#89
• ENH Use class name instead of self silverstripe-documentconverter#83
• ENH Use class name instead of self silverstripe-environmentcheck#104
• ENH Use class name instead of self silverstripe-errorpage#110
• ENH Use class name instead of self silverstripe-event-dispatcher#25
• ENH Use class name instead of self silverstripe-externallinks#129
• ENH Use class name instead of self silverstripe-framework#11270
• ENH Use class name instead of self silverstripe-frameworktest#183
• ENH Use class name instead of self silverstripe-graphql#590
• ENH Use class name instead of self silverstripe-hybridsessions#106
• ENH Use class name instead of self silverstripe-ldap#80
• ENH Use class name instead of self silverstripe-linkfield#295
• ENH Use class name instead of self silverstripe-login-forms#181
• ENH Use class name instead of self silverstripe-lumberjack#152
• ENH Use class name instead of self markdown-php-codesniffer#10
• ENH Use class name instead of self silverstripe-mfa#545
• ENH Use class name instead of self MinkFacebookWebDriver#27
• ENH Use class name instead of self silverstripe-realme#144
• ENH Use class name instead of self recipe-plugin#43
• ENH Use class name instead of self silverstripe-reports#184
• ENH Use class name instead of self silverstripe-restfulserver#127
• ENH Use class name instead of self silverstripe-securityreport#81
• ENH Use class name instead of self silverstripe-session-manager#198
• ENH Use class name instead of self silverstripe-sharedraftcontent#238
• ENH Use class name instead of self silverstripe-siteconfig#164
• ENH Use class name instead of self silverstripe-sitewidecontent-report#92
• ENH Use class name instead of self silverstripe-spamprotection#118
• ENH Use class name instead of self silverstripe-staticpublishqueue#192
• ENH Use class name instead of self silverstripe-subsites#575
• ENH Use class name instead of self silverstripe-tagfield#291
• ENH Use class name instead of self silverstripe-testsession#90
• ENH Use class name instead of self silverstripe-textextraction#95
• ENH Use class name instead of self silverstripe-userforms#1299
• ENH Use class name instead of self vendor-plugin#78
• ENH Use class name instead of self silverstripe-versioned#449
• ENH Use class name instead of self silverstripe-versioned-admin#344
• ENH Use class name instead of self silverstripe-versionfeed#111
• ENH Use class name instead of self silverstripe-webauthn-authenticator#183
• ENH Use class name instead of self symbiote/silverstripe-advancedworkflow#537
• ENH Use class name instead of self symbiote/silverstripe-gridfieldextensions#402
• ENH Use class name instead of self symbiote/silverstripe-queuedjobs#432
• ENH Use class name instead of self tractorcow-farm/silverstripe-fluent#859
• ENH Use self::class::method() syntax silverstripe-graphql#592

[maxime-rainville]

Is there an actual issue that got cause by this? e.g. Did we have a scenario where we called self::get() in Link wanting to query all Links and ended up querying only FileLink.

[GuySartorelli]

Is there an actual issue that got cause by this?

Yes. I'll link you the slack thread.

[GuySartorelli]

PRs merged.
I've raised silverstripe/silverstripe-standards#8 to add a rule in CI to catch this happening in the future.