create a method for indicating if a capability can be customized

Currently the only capability that cannot be customized are the core
boot ones, but (a) that will change (b) it obscures the intent of the
check.

subiquity/client/controllers/filesystem.py

@@ -300,7 +300,7 @@ class FilesystemController(SubiquityTuiController, FilesystemManipulator):
         # before the kinetic release. This is also similar to what we did for
         # https://launchpad.net/bugs/1962205
         coro = self.endpoint.guided.POST(choice)
-        if self.core_boot_capability is not None:
+        if not choice.capability.supports_manual_customization():
             self.app.next_screen(coro)
             return
         status = await self.app.wait_with_progress(coro)

subiquity/common/types.py

@@ -341,6 +341,14 @@ class GuidedCapability(enum.Enum):
                         GuidedCapability.CORE_BOOT_PREFER_ENCRYPTED,
                         GuidedCapability.CORE_BOOT_PREFER_UNENCRYPTED]
 
+    def supports_manual_customization(self) -> bool:
+        # After posting this capability to guided_POST, is it possible
+        # for the user to customize the layout further?
+        return self in [GuidedCapability.MANUAL,
+                        GuidedCapability.DIRECT,
+                        GuidedCapability.LVM,
+                        GuidedCapability.LVM_LUKS]
+
 
 class GuidedDisallowedCapabilityReason(enum.Enum):
     TOO_SMALL = enum.auto()

subiquity/server/controllers/filesystem.py

@@ -788,7 +788,7 @@ class FilesystemController(SubiquityController, FilesystemManipulator):
     async def guided_POST(self, data: GuidedChoiceV2) -> StorageResponse:
         log.debug(data)
         await self.guided(data)
-        if data.capability.is_core_boot():
+        if not data.capability.supports_manual_customization():
             await self.configured()
         return self._done_response()