[Improvement] [LDAP] Config value should return real null instead of 'null' string

[huage1994]

Purpose of the pull request

Currently if LDAP Config value is not set, DS would get String "null" as default value instead of real null currently. #11324 This PR is to fix this problem.

Brief change log

Verify this pull request

This pull request is already covered by existing tests, such as (please describe tests). dolphinscheduler/dolphinscheduler-api/src/test/java/org/apache/dolphinscheduler/api/security/impl/ldap/LdapServiceTest.java

[codecov-commenter]

Codecov Report

Merging #11325 (aef123e) into dev (caa6287) will increase coverage by 0.12%. The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev   #11325      +/-   ##
============================================
+ Coverage     40.13%   40.26%   +0.12%     
+ Complexity     4948     4844     -104     
============================================
  Files           988      974      -14     
  Lines         37721    37323     -398     
  Branches       4148     4141       -7     
============================================
- Hits          15140    15027     -113     
+ Misses        21038    20751     -287     
- Partials       1543     1545       +2     

Impacted Files	Coverage Δ
...nscheduler/api/security/impl/ldap/LdapService.java	6.38% <ø> (ø)
...olphinscheduler/plugin/task/emr/EmrParameters.java	0.00% <0.00%> (-50.00%)	:arrow_down:
...heduler/plugin/task/jupyter/JupyterParameters.java	33.33% <0.00%> (-46.67%)	:arrow_down:
...inscheduler/server/worker/config/WorkerConfig.java	0.00% <0.00%> (-46.16%)	:arrow_down:
...duler/plugin/task/zeppelin/ZeppelinParameters.java	33.33% <0.00%> (-36.67%)	:arrow_down:
...inscheduler/server/master/config/MasterConfig.java	0.00% <0.00%> (-33.34%)	:arrow_down:
...heduler/plugin/task/chunjun/ChunJunParameters.java	46.15% <0.00%> (-29.71%)	:arrow_down:
...che/dolphinscheduler/api/python/PythonGateway.java	17.82% <0.00%> (-1.99%)	:arrow_down:
...che/dolphinscheduler/alert/AlertSenderService.java	50.73% <0.00%> (-1.15%)	:arrow_down:
.../org/apache/dolphinscheduler/common/Constants.java	83.33% <0.00%> (ø)
... and 62 more

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[sonarqubecloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[huage1994]

Hello @EricGao888 @caishunfeng @SbloodyS , is there anybody can help review and merge the PR?

[SbloodyS]

Thanks for your contribution. This is a good beginning. Considering that it's your first contribution, I think we can get deep communication, you can contact me through mail or add WeChat(SbloodyS), when mail or added, please tell me who you are. I think I can help to familiar with the Dolphinscheduler if you meet with problems. @huage1994

[huage1994]

Thanks for your contribution. This is a good beginning. Considering that it's your first contribution, I think we can get deep communication, you can contact me through mail or add WeChat(SbloodyS), when mail or added, please tell me who you are. I think I can help to familiar with the Dolphinscheduler if you meet with problems. @huage1994

Fine. Thx a lot!