Perform same check on character validity in pathIdentifier that identifier does

Author: Mikah Chapman

core/model/src/main/kotlin/au/com/dius/pact/core/model/PathExpressions.kt

@@ -92,7 +92,7 @@ fun pathIdentifier(
     val ch = chars.next()
     when {
       ch.value == '*' -> tokens.add(PathToken.Star)
-      ch.value.isLetterOrDigit() || ch.value == '_' -> identifier(ch.value, chars, tokens, path)
+      ch.value.isLetterOrDigit() || EXP_ALLOWED_SPECIAL_CHARS.contains(ch.value) -> identifier(ch.value, chars, tokens, path)
       else -> throw InvalidPathExpression("Expected either a \"*\" or path identifier in path expression \"$path\"" +
         " at index ${ch.index}")
     }

core/model/src/test/groovy/au/com/dius/pact/core/model/PathExpressionsSpec.groovy

@@ -90,6 +90,8 @@ class PathExpressionsSpec extends Specification {
     where:
 
     expression                            | result
+    '$.container_records.example-ABC'     | [PathToken.Root.INSTANCE, new PathToken.Field('container_records'), new PathToken.Field('example-ABC')]
+    '$.container_records.example_ABC'     | [PathToken.Root.INSTANCE, new PathToken.Field('container_records'), new PathToken.Field('example_ABC')]
     '$.container_records.example:ABC'     | [PathToken.Root.INSTANCE, new PathToken.Field('container_records'), new PathToken.Field('example:ABC')]
     "\$.container_records['example:ABC']" | [PathToken.Root.INSTANCE, new PathToken.Field('container_records'), new PathToken.Field('example:ABC')]
     "\$.container_records['example/ABC']" | [PathToken.Root.INSTANCE, new PathToken.Field('container_records'), new PathToken.Field('example/ABC')]