feat: remove erasers in graphic context

Memola/Canvas/Contexts/GraphicContext.swift

@@ -160,7 +160,7 @@ extension GraphicContext {
                 thickness: pen.thickness
             )
             eraserStroke.graphicContext = self
-            withPersistence(\.backgroundContext) { [graphicContext = object, _stroke = eraserStroke] context in
+            withPersistence(\.backgroundContext) { [_stroke = eraserStroke] context in
                 let stroke = EraserObject(\.backgroundContext)
                 stroke.bounds = _stroke.bounds
                 stroke.color = _stroke.color
@@ -169,8 +169,6 @@ extension GraphicContext {
                 stroke.createdAt = _stroke.createdAt
                 stroke.quads = []
                 stroke.strokes = .init()
-                stroke.graphicContext = graphicContext
-                graphicContext?.erasers.add(stroke)
                 _stroke.object = stroke
                 try context.saveIfNeeded()
             }

Memola/Canvas/Geometries/Stroke/Strokes/PenStroke.swift

@@ -65,7 +65,7 @@ final class PenStroke: Stroke, @unchecked Sendable {
             bounds: object.bounds,
             color: object.color,
             style: style,
-            createdAt: object.createdAt,
+            createdAt: object.createdAt, // sometimes crash here
             thickness: object.thickness
         )
         self.object = object

Memola/Features/Memos/MemosView.swift

@@ -85,7 +85,6 @@ struct MemosView: View {
 
         let graphicContextObject = GraphicContextObject(\.viewContext)
         graphicContextObject.strokes = []
-        graphicContextObject.erasers = .init()
 
         memoObject.canvas = canvasObject
         memoObject.tool = toolObject

Memola/Persistence/Objects/EraserObject.swift

@@ -17,5 +17,4 @@ final class EraserObject: NSManagedObject {
     @NSManaged var thickness: CGFloat
     @NSManaged var quads: NSMutableOrderedSet
     @NSManaged var strokes: NSMutableSet
-    @NSManaged var graphicContext: GraphicContextObject?
 }

Memola/Persistence/Objects/GraphicContextObject.swift

@@ -12,5 +12,4 @@ import Foundation
 final class GraphicContextObject: NSManagedObject {
     @NSManaged var canvas: CanvasObject?
     @NSManaged var strokes: NSMutableOrderedSet
-    @NSManaged var erasers: NSMutableSet
 }

Memola/Resources/Models/MemolaModel.xcdatamodeld/MemolaModel.xcdatamodel/contents

@@ -12,13 +12,11 @@
         <attribute name="createdAt" attributeType="Date" usesScalarValueType="NO"/>
         <attribute name="style" attributeType="Integer 16" defaultValueString="0" usesScalarValueType="YES"/>
         <attribute name="thickness" attributeType="Double" defaultValueString="0.0" usesScalarValueType="YES"/>
-        <relationship name="graphicContext" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="GraphicContextObject" inverseName="erasers" inverseEntity="GraphicContextObject"/>
         <relationship name="quads" toMany="YES" deletionRule="Cascade" ordered="YES" destinationEntity="QuadObject" inverseName="eraser" inverseEntity="QuadObject"/>
         <relationship name="strokes" toMany="YES" deletionRule="Nullify" destinationEntity="StrokeObject" inverseName="erasers" inverseEntity="StrokeObject"/>
     </entity>
     <entity name="GraphicContextObject" representedClassName="GraphicContextObject" syncable="YES">
         <relationship name="canvas" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="CanvasObject" inverseName="graphicContext" inverseEntity="CanvasObject"/>
-        <relationship name="erasers" toMany="YES" deletionRule="Cascade" destinationEntity="EraserObject" inverseName="graphicContext" inverseEntity="EraserObject"/>
         <relationship name="strokes" toMany="YES" deletionRule="Cascade" ordered="YES" destinationEntity="StrokeObject" inverseName="graphicContext" inverseEntity="StrokeObject"/>
     </entity>
     <entity name="MemoObject" representedClassName="MemoObject" syncable="YES">