+ Badges introduction to database schemas

+ Adding some default empty list values where applicable
neighbors now has a default value of '[]' to enforce the "empty list" constraint on that field

json-api/migrations/2020-03-11-005217_channels/up.sql

@@ -4,5 +4,6 @@ CREATE TABLE IF NOT EXISTS `channels` (
     `name` VARCHAR(255) NOT NULL,
     `description` VARCHAR(2048),
     `kind` INTEGER NOT NULL,
+    `badges` VARCHAR(2048) DEFAULT '[]',
     PRIMARY KEY(`id`), UNIQUE KEY(`name`)
 );