fix: Allow Auto event duration is empty

[weichou1229]

Auto event duration should allow empty because the Core Metadata will apply the default value if duration is empty.

Close #987

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PR Checklist

Please check if your PR fulfills the following requirements:

• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• I am not introducing a new dependency (add notes below if you are)
• I have added unit tests for the new feature or bug fix (if not, why?) not impact
• I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• I have opened a PR for the related docs change (if not, why?) not impact

Testing Instructions

Test core metadata API with empty duration like below

curl 'http://localhost:59881/api/v3/device' \
--header 'Content-Type: application/json' \
--data '[{
    "device": {
      "name": "testDevice",
      "adminState": "UNLOCKED",
      "operatingState": "UP",
      "location": {},
      "serviceName": "device-virtual",
      "profileName": "Random-Boolean-Device",
      "autoEvents": [
        { "interval": "1s", "onChange": false, "sourceName": "Bool", 
       "retention": {"maxCap": 2000, "minCap": 1000, "duration":""}}
      ],
      "protocols": {
        "other": {}
        }
    },
    "apiVersion":"v3"
  }]
'

New Dependency Instructions (If applicable)

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.95%. Comparing base (db8453d) to head (a5c1c90).

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #988   +/-   ##
=======================================
  Coverage   42.95%   42.95%           
=======================================
  Files         119      119           
  Lines        7206     7206           
=======================================
  Hits         3095     3095           
  Misses       3768     3768           
  Partials      343      343           

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[judehung]

LGTM

[judehung]

@cloudxxx8 Do we need to release a new version of contracts for odessa due to this PR?

[cloudxxx8]

LGTM

[cloudxxx8]

@weichou1229 please pick this commit to the odesa branch