Create backend skeleton

backend/dataaccess/build.gradle

@@ -0,0 +1,13 @@
+dependencies {
+
+    implementation 'org.springframework.boot:spring-boot-starter-cache'
+    implementation 'org.springframework.boot:spring-boot-starter-validation'
+    implementation 'org.springframework.boot:spring-boot-starter-data-redis'
+    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
+    implementation 'org.springframework.boot:spring-boot-starter-data-rest'
+
+    runtimeOnly 'mysql:mysql-connector-java'
+    runtimeOnly 'com.h2database:h2'
+
+    implementation 'com.github.f4b6a3:uuid-creator:4.3.1'
+}

backend/dataaccess/src/main/java/eu/okaeri/timings/dataaccess/util/UUID6Generator.java

@@ -0,0 +1,38 @@
+package eu.okaeri.timings.dataaccess.util;
+
+import com.github.f4b6a3.uuid.UuidCreator;
+import org.hibernate.HibernateException;
+import org.hibernate.MappingException;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+import org.hibernate.id.UUIDGenerator;
+import org.hibernate.service.ServiceRegistry;
+import org.hibernate.type.Type;
+import org.hibernate.type.descriptor.java.UUIDTypeDescriptor;
+
+import java.io.Serializable;
+import java.util.Properties;
+import java.util.UUID;
+
+public class UUID6Generator extends UUIDGenerator {
+
+    private UUIDTypeDescriptor.ValueTransformer valueTransformer;
+
+    @Override
+    public void configure(Type type, Properties params, ServiceRegistry serviceRegistry) throws MappingException {
+        if (UUID.class.isAssignableFrom(type.getReturnedClass())) {
+            this.valueTransformer = UUIDTypeDescriptor.PassThroughTransformer.INSTANCE;
+        } else if (String.class.isAssignableFrom(type.getReturnedClass())) {
+            this.valueTransformer = UUIDTypeDescriptor.ToStringTransformer.INSTANCE;
+        } else {
+            if (!byte[].class.isAssignableFrom(type.getReturnedClass())) {
+                throw new HibernateException("Unanticipated return type [" + type.getReturnedClass().getName() + "] for UUID conversion");
+            }
+            this.valueTransformer = UUIDTypeDescriptor.ToBytesTransformer.INSTANCE;
+        }
+    }
+
+    @Override
+    public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
+        return this.valueTransformer.transform(UuidCreator.getTimeOrderedWithRandom());
+    }
+}