appAddonConfigs: change value to TEXT

since the value is used directly as an environment variable, we have to
allow up to max env var size (32767). Use TEXT which has a size of 64k

migrations/schema.sql

@@ -117,7 +117,7 @@ CREATE TABLE IF NOT EXISTS appAddonConfigs(
     appId VARCHAR(128) NOT NULL,
     addonId VARCHAR(32) NOT NULL,
     name VARCHAR(128) NOT NULL,
-    value VARCHAR(512) NOT NULL,
+    value TEXT NOT NULL,
     FOREIGN KEY(appId) REFERENCES apps(id));
 
 CREATE TABLE IF NOT EXISTS appEnvVars(