♻️ Refactor Zero.Companion.orThrow(String) method

This commit adds the `ErrorMessage.invalidZero(String)` internal method for dealing with invalid inputs.

subprojects/internal/src/commonMain/kotlin/org/kotools/types/internal/ErrorMessage.kt

@@ -11,4 +11,11 @@ public object ErrorMessage {
      */
     public fun invalidZero(number: Number): String =
         "'$number' shouldn't be other than zero."
+
+    /**
+     * Returns an error message indicating that the specified [text] is not a
+     * valid representation of zero.
+     */
+    public fun invalidZero(text: String): String =
+        "'$text' is not a valid representation of zero."
 }

subprojects/library/src/commonMain/kotlin/org/kotools/types/Zero.kt

@@ -1000,9 +1000,7 @@ public class Zero {
         @JvmStatic
         public fun orThrow(text: String): Zero {
             val regex = Regex("""^0+(?:\.0+)?$""")
-            require(text matches regex) {
-                "'$text' is not a valid representation of zero."
-            }
+            require(text matches regex) { ErrorMessage.invalidZero(text) }
             return Zero()
         }
     }

subprojects/library/src/commonTest/kotlin/org/kotools/types/ZeroCompanionTest.kt

@@ -221,7 +221,7 @@ class ZeroCompanionTest {
                 val exception: IllegalArgumentException =
                     assertFailsWith { Zero.orThrow(it) }
                 val actual: String? = exception.message
-                val expected = "'$it' is not a valid representation of zero."
+                val expected: String = ErrorMessage.invalidZero(it)
                 assertEquals(expected, actual)
             }
 }