demo: add iron examples

modules/x-demo/src/main/scala/demo/IronDemo.scala

@@ -0,0 +1,55 @@
+package demo
+
+import trading.domain.IronCatsInstances.given
+
+import cats.*
+import cats.data.EitherNel
+import cats.derived.*
+import cats.syntax.all.*
+import io.circe.*
+import io.circe.syntax.*
+import io.github.iltotore.iron.{ given, * }
+import io.github.iltotore.iron.circeSupport.given
+import io.github.iltotore.iron.constraint.any.DescribedAs
+import io.github.iltotore.iron.constraint.numeric.given
+import io.github.iltotore.iron.constraint.numeric.{ Greater, Less }
+import io.github.iltotore.iron.constraint.string.given
+import io.github.iltotore.iron.constraint.string.{ Alphanumeric, MaxLength, MinLength }
+
+type AgeR = DescribedAs[
+  Greater[0] & Less[151],
+  "Alien's age must be an integer between 1 and 150"
+]
+
+type NameR = DescribedAs[
+  Alphanumeric & MinLength[1] & MaxLength[50],
+  "Alien's name must be an alphanumeric of max length 50"
+]
+
+// format: off
+case class Alien(
+    name: String :| NameR,
+    age: Int :| AgeR
+) derives Codec.AsObject, Eq, Show
+// format: on
+
+// TODO: Remove this once this PR lands: https://github.com/Iltotore/iron/pull/68
+extension [A](value: A)
+  inline def refineNel[B](using inline constraint: Constraint[A, B]): EitherNel[String, A :| B] =
+    Either.cond(constraint.test(value), value.asInstanceOf[A :| B], constraint.message).toEitherNel
+
+object Alien:
+  def make(
+      name: String,
+      age: Int
+  ): EitherNel[String, Alien] =
+    (
+      name.refineNel[NameR],
+      age.refineNel[AgeR]
+    ).parMapN(Alien.apply)
+
+@main def ironDemo =
+  val alien = Alien("Bob", 120)
+  println(alien.asJson.noSpaces)
+  val runtime = Alien.make("", 0)
+  println(runtime)