[Integrated] RFR: Make the rest request error transform optional

[Robin Westberg]

Changeset: 0e9e8412
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2020-02-24 13:32:02 +0000
URL:       https://git.openjdk.java.net/skara/commit/0e9e8412

Make the rest request error transform optional

Reviewed-by: ehelin

! forge/src/main/java/org/openjdk/skara/forge/github/GitHubHost.java
! forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java
! forge/src/main/java/org/openjdk/skara/forge/gitlab/GitLabHost.java
! forge/src/main/java/org/openjdk/skara/forge/gitlab/GitLabRepository.java
! issuetracker/src/main/java/org/openjdk/skara/issuetracker/jira/JiraHost.java
! issuetracker/src/main/java/org/openjdk/skara/issuetracker/jira/JiraProject.java
! network/src/main/java/org/openjdk/skara/network/RestRequest.java
! network/src/test/java/org/openjdk/skara/network/RestRequestTests.java