imapc_sasl_mechanisms: Document supported values

Author: cmouse

data/settings.js

@@ -6583,7 +6583,23 @@ imapc_sasl_mechanisms {
   plain = yes
   login = yes
 }
-\`\`\``
+\`\`\`
+
+Supported mechanisms are:
+
+ * ANONYMOUS
+ * EXTERNAL
+ * LOGIN
+ * OAUTHBEARER
+ * PLAIN
+ * SCRAM-SHA-1
+ * SCRAM-SHA-1-PLUS
+ * SCRAM-SHA-256
+ * SCRAM-SHA-256-PLUS
+ * XOAUTH2
+
+Note that [[setting,imapc_password]] is ignored for \`ANONYMOUS\` and \`EXTERNAL\` mechanisms.
+For \`OAUTHBEARER\` and \`XOAUTH2\` [[setting,imapc_password]] should be bearer token.`
 	},
 
 	imapc_ssl: {
@@ -6629,7 +6645,8 @@ Only used if [[setting,imapc_ssl]] is enabled.`
 The user identity to be used for performing a regular IMAP LOGIN to the
 source IMAP server.
 
-[[variable,mail-user]] can be used.`
+[[variable,mail-user]] can be used. See also [[setting,imapc_sasl_mechanisms]].
+`
 	},
 
 	import_environment: {