FingerJointSettings: Make angle a class property

Don't allow the users to tinker with it. It is for internal use only.

Related: #627

boxes/edges.py

@@ -268,6 +268,8 @@ def setValues(self, thickness, relative: bool = True, **kw):
                 self.values[name] = value
             elif name in self.relative_params:
                 self.values[name] = value * factor
+            elif hasattr(self, name):
+                setattr(self, name, value)
             else:
                 raise ValueError(f"Unknown parameter for {self.__class__.__name__}: {name}")
         self.checkValues()
@@ -837,7 +839,6 @@ class FingerJointSettings(Settings):
 * absolute
   * style : "rectangular" : style of the fingers
   * surroundingspaces : 2.0 : space at the start and end in multiple of normal spaces
-  * angle: 90 : Angle of the walls meeting
 
 * relative (in multiples of thickness)
 
@@ -853,7 +854,6 @@ class FingerJointSettings(Settings):
     absolute_params = {
         "style": ("rectangular", "springs", "barbs", "snap"),
         "surroundingspaces": 2.0,
-        "angle": 90.0,
     }
 
     relative_params = {
@@ -866,6 +866,8 @@ class FingerJointSettings(Settings):
         "bottom_lip": 0.0,
     }
 
+    angle = 90 # Angle of the walls meeting
+
     def checkValues(self) -> None:
         if abs(self.space + self.finger) < 0.1:
             raise ValueError("FingerJointSettings: space + finger must not be close to zero")