server: use json for API and internal storage

[xhebox]

Signed-off-by: xhe xw897002528@gmail.com

What problem does this PR solve?

Issue Number: ref #11

Problem Summary: Reduce assumption on what format the server will return or store.

What is changed and how it works: The server will process json only now. The cli is resposible to convert it from yaml to json or vice versa.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

./bin/weirctl namespace list
./bin/weirctl namespace get default
./bin/weirctl namespace put

• No code

Notable changes

• Has configuration change
• Has HTTP API interfaces change (Don't forget to add the declarative for API)
• Has weirctl change
• Other user behavior changes

Release note

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None