feat(164): specify create overwrites soft deleted

To help ensure that declarative clients do not have a
degraded user experience with resources that implement 
soft-delete, specify that create overwrites an existing
soft-deleted resource.

This ensures that a declarative tool can still properly
apply a resource, overwriting it instead of requiring an
out of band force delete or having the user modify the
ID of the resource.

fixes #111 (which includes some significant debate and
context on why this approach was chosen).

Author: toumorokoshi

aep/general/0121/aep.md.j2

@@ -106,8 +106,7 @@ Examples of strong consistency include:
   get request for a resource **must** return the final values from the update
   request.
 - Following a successful delete that is the latest mutation on a resource, a
-  get request for a resource **must** return `NOT_FOUND` (or the resource with
-  the `DELETED` state value in the case of [soft delete][])
+  get request for a resource **must** return `NOT_FOUND`.
 
 Clients of resource-oriented APIs often need to orchestrate multiple operations
 in sequence (e.g., create resource A, create resource B which depends on A),

aep/general/0164/aep.md.j2

@@ -60,20 +60,19 @@ A resource that supports soft delete **should** provide an `Undelete` method:
 
 {% endtabs %}
 
-### Long-running undelete
+### Create
 
-Some resources take longer to undelete a resource than is reasonable for a
-regular API request. In this situation, the API **should** follow the
-long-running request pattern AEP-151.
+If a user attempts a create on a soft-deleted resource, the request **must**
+succeed, acting as if the resource did not exist previously.
 
 ### List and Get
 
-Soft-deleted resources **should not** be returned in `List` AEP-132 responses
-by default (unless `bool show_deleted` is true).
+Soft-deleted resources **must not** be returned in `List` AEP-132 responses by
+default (unless `bool show_deleted` is true).
 
-A `Get` AEP-131 request for a soft deleted resource **should** error with
-`410 Gone` unless `bool show_deleted` is true, in which case soft-deleted
-resources **must** return the resource.
+A `Get` AEP-131 request for a soft deleted resource **must** return with a
+`410 Gone` response unless `bool show_deleted` is true, in which case
+soft-deleted resources **must** return the resource.
 
 Services that soft delete resources **may** choose a reasonable strategy for
 purging those resources, including automatic purging after a reasonable time
@@ -84,9 +83,6 @@ removed.
 
 ### Declarative-friendly resources
 
-A resource that is declarative-friendly AEP-128 **should** support soft delete
-and undelete.
-
 **Important:** There is an ambiguity in declarative tooling between "create"
 and "undelete". When given an alias which was previously deleted and a
 directive to make it exist, tooling usually does not know if the intent is to
@@ -96,27 +92,17 @@ a new resource: the only way to undelete is to explicitly use the undelete RPC
 (an imperative operation), and declarative tools **may** elect not to map
 anything to undelete at all.
 
-Declarative-friendly resources **must** use long-running operations for both
-soft delete and undelete. The service **may** return an LRO that is already set
-to done if the request is effectively immediate.
-
-Declarative-friendly resources **must** include `validate_only` AEP-163 and
-`etag` AEP-154 in their `Undelete` methods.
-
 ### Errors
 
-If the user does not have permission to access the resource, regardless of
-whether or not it exists, the service **must** error with `403 Forbidden`.
-Permission **must** be checked prior to checking if the resource exists.
+Also see [errors](/errors) for additional guidance.
 
 If the user does have proper permission, but the requested resource does not
 exist (either it was never created or already expunged), the service **must**
 error with `404 Not Found`.
 
 If the user calling a soft `Delete` has proper permission, but the requested
 resource is already deleted, the service **must** succeed if `allow_missing` is
-`true`, and **should** error with `404 Not Found` if `allow_missing` is
-`false`.
+`true`, and **must** error with `404 Not Found` if `allow_missing` is `false`.
 
 If the user calling `Undelete` has proper permission, but the requested
 resource is not deleted, the service **must** error with `409 Conflict`.