(tested) refactor code

* add sentinel master parameter into driver config
* replace yaml double deserialization with `mapstructure` in initializers
* replace struct initializers with registered functions
* add torrent approval MD and a sanitize rest MDs

docs/middleware/interval_variation.md

@@ -28,10 +28,10 @@ An example config might look like this:
 
 ```yaml
 mochi:
-  prehooks:
-    - name: interval variation
-      config:
-        modify_response_probability: 0.2
-        max_increase_delta: 60
-        modify_min_interval: true
+    prehooks:
+        -   name: interval variation
+            config:
+                modify_response_probability: 0.2
+                max_increase_delta: 60
+                modify_min_interval: true
 ```

docs/middleware/torrent_approval.md

@@ -0,0 +1,64 @@
+# Approved torrents list
+
+Package `torrentapproval` can be used for only allow or block
+specified hashes or block specified hashes.
+
+## Functionality
+
+As said above, there are two modes of approval: white list and black list.
+
+If mode is **white list** (`invert` set to `false`), tracker works in
+_semi-private_ mode, which means, than peers can could share and receive info
+about only specified list of torrents' hashes.
+
+I.e.: if configuration contains hash `AAAA`, but peer announces hash `BBBB`
+tracker will return `unapproved torrent` message back to peer.
+
+If mode is **black list** (`invert` set to `true`), tracker will allow all hashes
+**except** specified.
+
+## Hash sources
+
+There are two sources of hashes: `list` and `directory`.
+
+Both of them used as **INITIAL** source for storing in storage.
+If storage is not `memory`, records are persisted until _somebody_
+or _something_ (different tool with access to storage) won't delete it.
+
+`list` is the static set of hashes, specified in configuration file.
+
+`directory` will watch for `*.torrent` files in specified path and
+append/delete records from storage. This source will parse all existing
+files at start and then watch for new files to add, or for delete events
+to remove hash from storage.
+
+## Configuration
+
+This middleware provides the following parameters for configuration:
+
+- `initial_source` - source type: `list` or `directory`
+- `configuration` - options for specified source
+	- `list`:
+		- `hash_list` - list of HEX encoded hashes
+		- `invert` - working mode: `true` - black list, `false` - white list
+		- `storage_ctx` - name of storage _context_ where to store data.
+		  It may be redis hash key, DB table name etc.
+	- `directory`:
+		- `path` - directory to watch
+		- `invert` and `storage_ctx` has the same meanins as `list`'s options
+
+Configuration example:
+
+An example config might look like this:
+
+```yaml
+mochi:
+    prehooks:
+        -   name: torrent approval
+                options:
+                    initial_source: list
+                    configuration:
+                        hash_list: ["AAA", "BBB"]
+                        invert: false
+                        storage_ctx: APPROVED_HASH
+```