Make sure volume.depth for circular beds is forced to width

Both width and depth should be the diameter. Adjusted docs
accordingly to reflect this too.

docs/api/printerprofiles.rst

@@ -143,11 +143,12 @@ Profile
    * - ``volume.width``
      - 0..1
      - ``float``
-     - The width of the print volume
+     - The width of the print volume. For circular beds, the diameter of the bed.
    * - ``volume.depth``
      - 0..1
      - ``float``
-     - The depth of the print volume
+     - The depth of the print volume. For circular beds, this is the diameter of the bed and will be forced to be the same
+       as ``volume.width`` upon saving.
    * - ``volume.height``
      - 0..1
      - ``float``

src/octoprint/printer/profile.py

@@ -453,6 +453,10 @@ class PrinterProfileManager(object):
 		if profile["volume"]["formFactor"] == BedTypes.CIRCULAR and not profile["volume"]["origin"] == BedOrigin.CENTER:
 			profile["volume"]["origin"] = BedOrigin.CENTER
 
+		# force width and depth of volume to be identical for circular beds, with width being the reference
+		if profile["volume"]["formFactor"] == BedTypes.CIRCULAR:
+			profile["volume"]["depth"] = profile["volume"]["width"]
+
 		# validate offsets
 		offsets = []
 		for offset in profile["extruder"]["offsets"]:

src/octoprint/static/js/app/viewmodels/printerprofiles.js

@@ -281,6 +281,10 @@ $(function() {
                 }
             }
 
+            if (profile.volume.formFactor == "circular") {
+                profile.volume.depth = profile.volume.width;
+            }
+
             return profile;
         };