make registration regex more universal (#181)

* make registration regex more universal

* misspell fix

circe-akka-serializer/src/main/scala/org/virtuslab/ash/circe/Register.scala

@@ -30,7 +30,17 @@ object Register {
   //noinspection LanguageFeature
   def REGISTRATION_REGEX: String = macro regexImpl
 
-  private val circeRegex = """org\.virtuslab\.ash\.circe\.Registration\[.*\]"""
+  /**
+   * `circeRegex` is the preferred typeRegexPattern for Circe Akka Serializer usage. It contains leading
+   * and trailing `.*` - so that it matches both single Registration and multiple Registrations in a collection.
+   * It is used by the codec-registration-checker-plugin to collect properly registered codecs.
+   *
+   * As codec-registration-checker-plugin searches for `circeRegex` occurrences in the generated AST - and detects
+   * proper registrations if detected type contains the regex - there might be some rare corner cases, where
+   * something like `Option[Register[User_Defined_Type]]` is in the AST and codec-registration-checker-plugin would
+   * still treat it as proper registration. However, such situations have not been encountered in real usages.
+   */
+  private val circeRegex = """.*org\.virtuslab\.ash\.circe\.Registration\[.*\].*"""
 
   def regexImpl(c: blackbox.Context): c.Expr[String] = {
     import c.universe._