Switch from npm to yarn (better supported in build agent)

Makefile

@@ -6,12 +6,12 @@ compile-java-quick: validate-spec;
 	mvn compile package -Dmaven.test.skip=true
 compile: clean compile-java;
 compile-quick: clean compile-java-quick;
-install-npm:;
-	npm ci
-generate-spec: install-npm;
-	npm run generate-json-schema
-validate-spec: install-npm;
-	npm run test
+install-yarn:;
+	yarn install --frozen-lockfile --audit
+generate-spec: install-yarn;
+	yarn run generate-json-schema
+validate-spec: install-yarn;
+	yarn run test
 compile-start: compile-quick;
 	docker-compose down
 	docker-compose build
@@ -21,7 +21,7 @@ compile-start-headless: compile-quick;
 	docker-compose build
 	docker-compose up -d
 start-spec: validate-spec;
-	npm run start
+	yarn run start
 generate-notice-src:;
 	docker run -v $(PWD)/:/project \
 		-v /project/node_modules \