Store dataset filters in the database

src/main/resources/db/migration/V5_2__AddDatasetFilters.sql

+--
+-- Name: query_covariable; Type: TABLE; Schema: public; Owner: postgres
+--
+
+CREATE TABLE query_training_datasets (
+    id bigint NOT NULL,
+    code character varying(255) NOT NULL
+);
+
+
+ALTER TABLE query_training_datasets OWNER TO postgres;
+
+ALTER TABLE ONLY query_training_datasets
+    ADD CONSTRAINT fk_query_training_datasets FOREIGN KEY (code) REFERENCES variable(code);
+
+
+CREATE TABLE query_testing_datasets (
+    id bigint NOT NULL,
+    code character varying(255) NOT NULL
+);
+
+
+ALTER TABLE query_testing_datasets OWNER TO postgres;
+
+ALTER TABLE ONLY query_testing_datasets
+    ADD CONSTRAINT fk_query_testing_datasets FOREIGN KEY (code) REFERENCES variable(code);
+
+CREATE TABLE query_validation_datasets (
+    id bigint NOT NULL,
+    code character varying(255) NOT NULL
+);
+
+
+ALTER TABLE query_validation_datasets OWNER TO postgres;
+
+ALTER TABLE ONLY query_validation_datasets
+    ADD CONSTRAINT fk_query_validation_datasets FOREIGN KEY (code) REFERENCES variable(code);