feat: add Pawn rule that lets it move one step forward.

chess/src/main/scala/io/github/chess/model/rules/pawn/ForwardOneRule.scala

@@ -0,0 +1,15 @@
+/*
+ * MIT License
+ * Copyright (c) 2023 Cesario Jahrim Gabriele & Derevyanchenko Maxim & Felice Mirko & Kentpayeva Madina
+ *
+ * Full license description available at: https://github.com/jahrim/PPS-22-chess/blob/master/LICENSE
+ */
+package io.github.chess.model.rules.pawn
+
+import io.github.chess.model.{Move, Position}
+import io.github.chess.model.rules.ChessRule
+
+/** Implementation of the Pawn rule that makes it move one step forward. */
+class ForwardOneRule extends ChessRule:
+
+  override def findMoves(position: Position): Set[Move] = Set(Move(position, position.rankUp()))

chess/src/test/scala/io/github/chess/model/rules/pawn/PawnRulesSpec.scala

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+/*
+ * MIT License
+ * Copyright (c) 2023 Cesario Jahrim Gabriele & Derevyanchenko Maxim & Felice Mirko & Kentpayeva Madina
+ *
+ * Full license description available at: https://github.com/jahrim/PPS-22-chess/blob/master/LICENSE
+ */
+package io.github.chess.model.rules.pawn
+
+import io.github.chess.AbstractSpec
+import io.github.chess.model.Position
+
+/** Test suit for all Pawn movement rules. */
+class PawnRulesSpec extends AbstractSpec:
+
+  val pawnInitialPosition: Position = (0, 1)
+  val pawnNextPosition: Position = (0, 2)
+
+  "The Forward rule" should "let move the pawn only to the following rank, without changing its file" in {
+    val oneStepRule = ForwardOneRule()
+    val moves = oneStepRule.findMoves(pawnInitialPosition)
+    moves should have size 1
+    all(moves) should have(Symbol("to")(pawnNextPosition))
+  }