fix(pkg/config): use storage endpoints

changes:
- Only one storage endpoint can be defined. This consists of a URL which
  can be used to specify whether the data is to be stored in a file or
  in a database.

pkg/storage/db/sql/psql/schema/v0.1.1.sql

@@ -0,0 +1,3 @@
+ALTER TABLE humidities ALTER COLUMN creation_date DROP NOT NULL;
+ALTER TABLE pressures ALTER COLUMN creation_date DROP NOT NULL;
+ALTER TABLE temperatures ALTER COLUMN creation_date DROP NOT NULL;