fix: get-subscription - various issues described below

* Controller needed @transactional. This did not show in the integration tests cos they already had @transactional wrapper on the @test which was a BAD IDEA
* Database event_types needed to be an array i.e. varchar(128)p[]. Puzzled why this did not show on the integrations tests
* Entity needs @Enumerated to ensure its saved as string. Might change this to database enum to avoid this
* Lack of exception handler meant some logging was not showing. We not have a global handler to log everything and rethrow
* Added the missing api-test which would have exhibited the error

Author: coling01

src/apiTest/java/uk/gov/hmcts/cp/subscription/http/SubscriptionApiTest.java

@@ -24,10 +24,10 @@ class SubscriptionApiTest {
 
     @Test
     void round_trip_subscription_should_work_ok() throws InterruptedException {
-        String postUrl = String.format("%s/client-subscriptions", baseUrl);
-        HttpHeaders headers = new HttpHeaders();
+        final String postUrl = java.lang.String.format("%s/client-subscriptions", baseUrl);
+        final HttpHeaders headers = new HttpHeaders();
         headers.setContentType(MediaType.APPLICATION_JSON);
-        String body = "{\"eventTypes\":[\"PCR\",\"CUSTODIAL_RESULT\"],\n" +
+        final String body = "{\"eventTypes\":[\"PCR\",\"CUSTODIAL_RESULT\"],\n" +
                 "\"notificationEndpoint\":{\"webhookUrl\":\"https://my-callback-url\"}}";
         final ResponseEntity<String> postResult = http.exchange(
                 postUrl,
@@ -38,12 +38,12 @@ void round_trip_subscription_should_work_ok() throws InterruptedException {
         System.out.println("postResult:" + postResult);
         assertThat(postResult.getStatusCode()).isEqualTo(HttpStatus.CREATED);
         assertThat(postResult.getBody()).contains("clientSubscriptionId");
-        String subscriptionId = postResult.getBody()
+        final String subscriptionId = postResult.getBody()
                 .replaceAll(".*clientSubscriptionId\":\"", "")
                 .replaceAll("\".*$", "");
 
         System.out.println("subscriptionId:" + subscriptionId);
-        String getUrl = String.format("%s/client-subscriptions/%s", baseUrl, subscriptionId);
+        final String getUrl = String.format("%s/client-subscriptions/%s", baseUrl, subscriptionId);
         final ResponseEntity<String> getResult = http.exchange(
                 getUrl,
                 HttpMethod.GET,