created classes table

server/db/schema/classes.sql

@@ -0,0 +1,13 @@
+CREATE TABLE IF NOT EXISTS public.classes
+(
+    id integer NOT NULL GENERATED ALWAYS AS IDENTITY ( INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1 ),
+    title VARCHAR(256) NOT NULL,
+    description TEXT,
+    location VARCHAR(256) NOT NULL,
+    capacity INT NOT NULL,
+    level character varying(16) COLLATE pg_catalog."default" NOT NULL,
+    costume TEXT NOT NULL,
+    CONSTRAINT class_pkey PRIMARY KEY (id),
+    CONSTRAINT level_check CHECK (level::text = ANY (ARRAY['beginner'::character varying, 'intermediate'::character varying, 'advanced'::character varying]::text[]))
+)
+