Deprecate special value 'auto' for attribute 'id' of compute_flavor

Across our modules we use the None values to mark default values for
module attributes. This is in line with openstacksdk's behaviour.

Change-Id: I5920aeeb8eef2ee1c2066a71a273ba52f02305c3

plugins/modules/compute_flavor.py

@@ -10,7 +10,8 @@ module: compute_flavor
 short_description: Manage OpenStack compute flavors
 author: OpenStack Ansible SIG
 description:
-   - Add or remove flavors from OpenStack.
+   - Add or remove compute flavors from OpenStack.
+   - Updating a flavor consists of deleting and (re)creating a flavor.
 options:
   state:
     description:
@@ -63,7 +64,10 @@ options:
        - ID for the flavor. This is optional as a unique UUID will be
          assigned if a value is not specified.
        - Note that this ID will only be used when first creating the flavor.
-    default: "auto"
+       - The ID of an existing flavor cannot be changed.
+       - When I(id) is set to C(auto), a new id will be autogenerated.
+         C(auto) is kept for backward compatibility and
+         will be dropped in the next major release.
     type: str
     aliases: ['flavorid']
   extra_specs:
@@ -201,7 +205,7 @@ class ComputeFlavorModule(OpenStackModule):
         swap=dict(default=0, type='int'),
         rxtx_factor=dict(default=1.0, type='float'),
         is_public=dict(default=True, type='bool'),
-        id=dict(default='auto', aliases=['flavorid']),
+        id=dict(aliases=['flavorid']),
         extra_specs=dict(type='dict'),
     )
 
@@ -251,24 +255,25 @@ class ComputeFlavorModule(OpenStackModule):
                 flavor, extra_specs, old_extra_specs))
 
         if state == 'present':
-            flavorid = self.params['id']
+            flavor_id = self.params['id']
+            # Keep for backward compatibility
+            flavor_id = None if flavor_id == 'auto' else flavor_id
             if flavor and self._needs_update(flavor):
                 # Because only flavor descriptions are updateable, we have to
                 # delete and recreate a flavor to "update" it
+                flavor_id = flavor['id']
                 self.conn.compute.delete_flavor(flavor)
                 old_extra_specs = {}
-                if flavorid == 'auto':
-                    flavorid = flavor['id']
                 flavor = None
 
             changed = False
             if not flavor:
-                flavor = self.conn.create_flavor(
+                flavor = self.conn.compute.create_flavor(
                     name=name,
                     ram=self.params['ram'],
                     vcpus=self.params['vcpus'],
                     disk=self.params['disk'],
-                    flavorid=flavorid,
+                    id=flavor_id,
                     ephemeral=self.params['ephemeral'],
                     swap=self.params['swap'],
                     rxtx_factor=self.params['rxtx_factor'],