RFR: 1256: Use stream api to simplify the csr issue lookup [v5]

[Erik Joelsson]

On Wed, 1 Dec 2021 19:01:48 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> Hi all,
>> 
>> This patch adds the common methods `Issue#linksWithRelationships`, `Issue#csrLink` and `Issue#csrIssue` and refactors the code to reduce the loop nested statements by using these common methods.
>> 
>> All the existing tests passed.
>> 
>> Best Regards,
>> -- Guoxiong
>
> Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix the situation  when the csr issue not existing. Revise the reply message.

Marked as reviewed by erikj (Lead).

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PR: https://git.openjdk.java.net/skara/pull/1248