feature #4: create function for follow

resources/tests/follow.sql

@@ -0,0 +1,56 @@
+do
+$$
+declare
+    created_user     json  := '{"username": "george", "plain_password": "azerty"}';
+    created_user2    json  := '{"username": "john", "plain_password": "qwerty"}';
+    _citizen_id      uuid;
+    _citizen_id2     uuid;
+    created_citizen json := $json$
+    {
+      "name": {
+        "first_name": "George",
+        "last_name": "MICHEL"
+      },
+      "birthday": "2001-01-01"
+    }
+    $json$;
+    created_citizen2 json := $json$
+    {
+      "name": {
+        "first_name": "John",
+        "last_name": "Doe"
+      },
+      "birthday": "2002-01-01"
+    }
+    $json$;
+begin
+    -- insert user for context
+    call insert_user(created_user);
+    call insert_user(created_user2);
+    created_citizen := jsonb_set(created_citizen::jsonb, '{user}'::text[], jsonb_build_object('id', created_user->>'id'), true)::json;
+    created_citizen2 := jsonb_set(created_citizen2::jsonb, '{user}'::text[], jsonb_build_object('id', created_user2->>'id'), true)::json;
+
+    -- insert new citizen for context
+    call upsert_citizen(created_citizen);
+    _citizen_id := created_citizen->>'id';
+    -- insert new citizen for context
+    call upsert_citizen(created_citizen2);
+    _citizen_id2 := created_citizen2->>'id';
+
+
+    perform follow('citizen'::regclass, _citizen_id, _citizen_id2);
+    assert (select count(*) > 0 from follow), 'follow must be inserted';
+
+    perform unfollow('citizen'::regclass, _citizen_id, _citizen_id2);
+    assert (select count(*) = 0 from follow), 'follow must be deleted after unfollow';
+
+    -- delete article and context
+    delete from citizen;
+    delete from "user";
+
+    raise notice 'follow test pass';
+end;
+$$;
+
+
+-- select uuid_generate_v4();