feat: Adds multi-step form to generate equivalent lengths for a project.

Tests/ApiRouteTests/ProjectRouteTests.swift

@@ -72,4 +72,34 @@ struct ProjectRouteTests {
     let route = try router.parse(&request)
     #expect(route == .project(.index))
   }
+
+  @Test
+  func formData() throws {
+    let p = Body {
+      FormData {
+        Optionally {
+          Field("id", default: nil) { EffectiveLength.ID.parser() }
+        }
+        Field("projectID") { Project.ID.parser() }
+        Field("name", .string)
+        Field("type") { EffectiveLength.EffectiveLengthType.parser() }
+        Many {
+          Field("straightLengths") {
+            Int.parser()
+          }
+        }
+      }
+      .map(.memberwise(SiteRoute.View.ProjectRoute.EquivalentLengthRoute.StepTwo.init))
+    }
+
+    var request = URLRequestData(
+      body: .init(
+        "projectID=15062A72-7AB5-4F15-9B1F-74A4BFA53CBB&name=Test&type=supply&straightLengths=20&straightLengths=10"
+          .utf8
+      )
+    )
+    let value = try p.parse(&request)
+    print(value)
+    #expect(value.straightLengths == [20, 10])
+  }
 }