docs reorg

docs/v0.3_sharing_modes.md

@@ -29,3 +29,19 @@ In `v0.3`, `zrok` will offer both a "public" and a "private" sharing mode. When
 `v0.3` introduces a "private" sharing mode. When provisioning a service for private sharing, `zrok` will not create any policies for the service, until a request for a frontend binding is created for the service (through the `zrok serve` command).
 
 The `v0.3` `zrok` service will support both identified users (the `zrok` user has a provisioned `environment`), as well as ephemeral users (the `zrok` controller will create an "ephemeral environment" for these users).
+
+## Backend Modes
+
+In `v0.2`, the only possible `backend` "mode" was for reverse proxying HTTP traffic to a local endpoint. The `v0.3` `zrok` client will support several different `backend` modes.
+
+### Web Mode
+
+A user has a collection of files on disk. Sharing with a `backend` mode of "web", will create a `backend` that shares a file tree as if it were a local web server.
+
+### DAV Mode
+
+A user wants to operate a read/write repository of files accessible through either conventional WebDAV clients (through `public` `frontend` instances), or through the `zrok` CLI.
+
+### Proxy Mode
+
+`v0.3` will retain the classic reverse proxy mode, as well.