+ * case you'll want to be looking at a \MediaWiki\Session\SessionProvider
+ * instead.)
+ *
+ * For account creation, the PrimaryAuthenticationProvider takes form data and
+ * stores some authentication details which will allow it to verify a login by
+ * that user in the future. This might for example involve saving it in the
+ * database in a table that can be joined to the user table, or sending it to
+ * some external service for account creation, or authenticating the user with
+ * some remote service and then recording that the remote identity is linked to
+ * the local account.
+ * The creation of the local user (i.e. calling User::addToDatabase()) is handled
+ * by AuthManager once the primary authentication provider returns a PASS
+ * from begin/continueAccountCreation; do not try to do it yourself.
+ *
+ * For account linking, the PrimaryAuthenticationProvider verifies the user's
+ * identity at some external service (typically by redirecting the user and
+ * asking the external service to verify) and then records which local account
+ * is linked to which remote accounts. It should keep track of this and be able
+ * to enumerate linked accounts via getAuthenticationRequests(ACTION_REMOVE).