only use @Transactional from Spring (not JavaX) and use readOnly=true where possible

src/main/java/net/hostsharing/hsadminng/hs/hscustomer/CustomerController.java

@@ -5,10 +5,10 @@ import net.hostsharing.hsadminng.generated.api.v1.api.CustomersApi;
 import net.hostsharing.hsadminng.generated.api.v1.model.CustomerResource;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder;
 
-import javax.transaction.Transactional;
 import java.util.List;
 import java.util.UUID;
 
@@ -26,7 +26,7 @@ public class CustomerController implements CustomersApi {
     private CustomerRepository customerRepository;
 
     @Override
-    @Transactional
+    @Transactional(readOnly = true)
     public ResponseEntity<List<CustomerResource>> listCustomers(
         String userName,
         String assumedRoles,

src/main/java/net/hostsharing/hsadminng/hs/hspackage/PackageController.java

@@ -7,9 +7,9 @@ import net.hostsharing.hsadminng.generated.api.v1.model.PackageResource;
 import net.hostsharing.hsadminng.generated.api.v1.model.PackageUpdateResource;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.RestController;
 
-import javax.transaction.Transactional;
 import java.util.List;
 import java.util.UUID;
 
@@ -26,7 +26,7 @@ public class PackageController implements PackagesApi {
     private PackageRepository packageRepository;
 
     @Override
-    @Transactional
+    @Transactional(readOnly = true)
     public ResponseEntity<List<PackageResource>> listPackages(
         String userName,
         String assumedRoles,

src/main/java/net/hostsharing/hsadminng/rbac/rbacgrant/RbacGrantController.java

@@ -2,16 +2,15 @@ package net.hostsharing.hsadminng.rbac.rbacgrant;
 
 import net.hostsharing.hsadminng.context.Context;
 import net.hostsharing.hsadminng.generated.api.v1.api.RbacgrantsApi;
-import net.hostsharing.hsadminng.generated.api.v1.api.RbacrolesApi;
 import net.hostsharing.hsadminng.generated.api.v1.model.RbacGrantResource;
-import net.hostsharing.hsadminng.generated.api.v1.model.RbacRoleResource;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder;
 
-import javax.transaction.Transactional;
 import java.util.List;
+import java.util.UUID;
 
 import static net.hostsharing.hsadminng.Mapper.map;
 import static net.hostsharing.hsadminng.Mapper.mapList;
@@ -27,7 +26,7 @@ public class RbacGrantController implements RbacgrantsApi {
     private RbacGrantRepository rbacGrantRepository;
 
     @Override
-    @Transactional
+    @Transactional(readOnly = true)
     public ResponseEntity<List<RbacGrantResource>> listUserGrants(
         final String currentUser,
         final String assumedRoles) {

src/main/java/net/hostsharing/hsadminng/rbac/rbacrole/RbacRoleController.java

@@ -5,9 +5,9 @@ import net.hostsharing.hsadminng.generated.api.v1.api.RbacrolesApi;
 import net.hostsharing.hsadminng.generated.api.v1.model.RbacRoleResource;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.RestController;
 
-import javax.transaction.Transactional;
 import java.util.List;
 
 import static net.hostsharing.hsadminng.Mapper.mapList;
@@ -23,7 +23,7 @@ public class RbacRoleController implements RbacrolesApi {
     private RbacRoleRepository rbacRoleRepository;
 
     @Override
-    @Transactional
+    @Transactional(readOnly = true)
     public ResponseEntity<List<RbacRoleResource>> listRoles(
         final String currentUser,
         final String assumedRoles) {

src/main/java/net/hostsharing/hsadminng/rbac/rbacuser/RbacUserController.java

@@ -6,11 +6,11 @@ import net.hostsharing.hsadminng.generated.api.v1.model.RbacUserPermissionResour
 import net.hostsharing.hsadminng.generated.api.v1.model.RbacUserResource;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder;
 
 import javax.persistence.EntityManager;
-import javax.transaction.Transactional;
 import java.util.List;
 import java.util.UUID;
 
@@ -48,7 +48,7 @@ public class RbacUserController implements RbacusersApi {
     }
 
     @Override
-    @Transactional
+    @Transactional(readOnly=true)
     public ResponseEntity<List<RbacUserResource>> listUsers(
         @RequestHeader(name = "current-user") final String currentUserName,
         @RequestHeader(name = "assumed-roles", required = false) final String assumedRoles,
@@ -62,7 +62,7 @@ public class RbacUserController implements RbacusersApi {
     }
 
     @Override
-    @Transactional
+    @Transactional(readOnly=true)
     public ResponseEntity<List<RbacUserPermissionResource>> listUserPermissions(
         @RequestHeader(name = "current-user") final String currentUserName,
         @RequestHeader(name = "assumed-roles", required = false) final String assumedRoles,