Ensure ApplicationKind only accept enum defined value

[khanhtc1202]

What this PR does:

as title

Why we need it:

Instead of not validating the ApplicationKind, which web form submitted to the API as preparation for pipedv1 managing application, we should mark this as accepting only defined enum value. With application managing by pipedv1, this field is not required, but the web form will send value 0 (kind: Kubernetes) as default; this field would not be used in any logic on the server side of piped side in case of v1 piped.

Which issue(s) this PR fixes:

Fllow #5517

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[Warashi]

👍🏻

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.43%. Comparing base (bdcc7a2) to head (891e02e).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5532      +/-   ##
==========================================
- Coverage   26.44%   26.43%   -0.01%     
==========================================
  Files         465      465              
  Lines       49858    49858              
==========================================
- Hits        13186    13182       -4     
- Misses      35618    35621       +3     
- Partials     1054     1055       +1     

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