fix #8135 add a default value to accessKeyId

[24kpure]

#8135

What is the purpose of the change

Reducing auth configuration

Brief changelog

Adding a default value to accessKeyId

Verifying this change

Checklist

• Make sure there is a GitHub_issue field for the change (usually before you start working on it). Trivial changes like typos do not require a GitHub issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Check if is necessary to patch to Dubbo 3 if you are work on Dubbo 2.7
• GitHub Actions works fine on your own branch.

[codecov-commenter]

Codecov Report

Merging #8136 (40d9515) into master (99ccb57) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #8136      +/-   ##
============================================
- Coverage     61.21%   61.20%   -0.02%     
  Complexity      490      490              
============================================
  Files          1090     1090              
  Lines         43944    43944              
  Branches       6418     6418              
============================================
- Hits          26902    26897       -5     
- Misses        14062    14066       +4     
- Partials       2980     2981       +1     

Impacted Files	Coverage Δ
...dubbo/remoting/exchange/support/DefaultFuture.java	82.05% <0.00%> (-5.13%)	⬇️
.../apache/dubbo/remoting/transport/AbstractPeer.java	58.69% <0.00%> (-4.35%)	⬇️
.../dubbo/remoting/transport/netty4/NettyChannel.java	61.38% <0.00%> (-2.98%)	⬇️
...etadata/report/support/AbstractMetadataReport.java	59.70% <0.00%> (-0.98%)	⬇️
...apache/dubbo/common/extension/ExtensionLoader.java	81.23% <0.00%> (+0.21%)	⬆️
...he/dubbo/registry/multicast/MulticastRegistry.java	70.23% <0.00%> (+0.93%)	⬆️
...o/remoting/transport/ChannelHandlerDispatcher.java	70.00% <0.00%> (+10.00%)	⬆️

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[AlbumenJ]

Was is necessary to add a default value? This might cause some compatible problem for other users.

[24kpure]

Fist of all,thanks for your advice.
It's not necessary to add a default value,but it does reduce some auth config which make no difference to result in most case。 As for compatible problem，as far as I am concerned, it works well when new users add new auth service config ,which thows AccessKeyNotFoundException in current version。Similarly，old users will not be in trouble for they have added the config for some time。