Store role list in database and convert role mentions into a readable format

database/upgrades/07-store-role-info.sql

@@ -0,0 +1,19 @@
+-- v7: Store role info
+CREATE TABLE role (
+    dc_guild_id TEXT,
+    dcid        TEXT,
+
+    name TEXT NOT NULL,
+    icon TEXT,
+
+    mentionable BOOLEAN NOT NULL,
+    managed     BOOLEAN NOT NULL,
+    hoist       BOOLEAN NOT NULL,
+
+    color       INTEGER NOT NULL,
+    position    INTEGER NOT NULL,
+    permissions BIGINT  NOT NULL,
+
+    PRIMARY KEY (dc_guild_id, dcid),
+    CONSTRAINT role_guild_fkey FOREIGN KEY (dc_guild_id) REFERENCES guild (dcid) ON DELETE CASCADE
+);