Add tagged services for import

- list services in /import
- add url to import service
- ImportBundle routing are now prefixed by /import
- optimize flush in each import (flushing each 20 contents)
- improve design of each import
- add more tests

src/Wallabag/ImportBundle/Resources/config/services.yml

@@ -1,4 +1,7 @@
 services:
+    wallabag_import.chain:
+        class: Wallabag\ImportBundle\Import\ImportChain
+
     wallabag_import.pocket.client:
         class: GuzzleHttp\Client
         arguments:
@@ -18,6 +21,8 @@ services:
         calls:
             - [ setClient, [ "@wallabag_import.pocket.client" ] ]
             - [ setLogger, [ "@logger" ]]
+        tags:
+            -  { name: wallabag_import.import, alias: pocket }
 
     wallabag_import.wallabag_v1.import:
         class: Wallabag\ImportBundle\Import\WallabagV1Import
@@ -25,3 +30,5 @@ services:
             - "@doctrine.orm.entity_manager"
         calls:
             - [ setLogger, [ "@logger" ]]
+        tags:
+            -  { name: wallabag_import.import, alias: wallabag_v1 }