Document new OAuth changes for 4.3.0 (#1445)

* Improve deprecation messaging for Application#vapid_key

* Format JSON examples in Instance methods

* Remove vapid_key from Apps API examples, since this property is deprecated on Application entity

* Add documentation for new OAuth 2.0 features added in 4.3.0

* Improve documentation for oauth-scopes

* Update content/en/api/oauth-scopes.md

Co-authored-by: Matt Jankowski <matt@jankowski.online>

* Update content/en/api/oauth-scopes.md

Co-authored-by: Matt Jankowski <matt@jankowski.online>

* Update content/en/api/oauth-scopes.md

Co-authored-by: Matt Jankowski <matt@jankowski.online>

* Update content/en/api/oauth-scopes.md

Co-authored-by: Matt Jankowski <matt@jankowski.online>

* Add deprecated and removed shortcode labels

* Use deprecated and removed shortcodes

* Improve OAuth documentation

* More OAuth documentation improvements

* Correct streaming API documentation after 4.2.0 changes

* Add note about improved Push Subscription API validation in 4.3.0

* Fix inconsistent OAuth label formatting

* Add note that there is a relationship between Accounts and the Application used to create them

* Add note that application registration endpoint also supports JSON bodies

* Be consistent in the formatting of placeholder values for Bearer tokens

* code review changes

* Slight changes in wording

* Add documentation for PKCE

* Removal of crypto oauth scope

* Cross-link authorization's scope with the OAuth Scopes documentation

* Update content/en/methods/oauth.md

* Update content/en/api/oauth-scopes.md

---------

Co-authored-by: Matt Jankowski <matt@jankowski.online>
Co-authored-by: David Roetzel <david@roetzel.de>

layouts/shortcodes/deprecated.html

@@ -0,0 +1 @@
+<span class="api-method-parameter-deprecated">{{ i18n "deprecated" }}</span>

layouts/shortcodes/removed.html

@@ -0,0 +1 @@
+<span class="api-method-parameter-removed">{{ i18n "removed" }}</span>