feat: support tags per operation

[liemle3893]

1. Fixed: Unquote can return error in case of input string is not quoted, let's return to original value as fall back.
2. Support tags per operation. Currently, operation inherit from group or swtags and their is no way to custom it. Example below.

info(
    title: "type title here"
    desc: "type desc here"
    author: "type author here"
    email: "type email here"
    version: "type version here"
)

import "sys/user.api"

@server(
  group: test
)
service user-api {
    @doc(
        summary: "注册"
        tags: "test,auth"
    )
    @handler register
    post /api/user/register (RegisterReq)
}

Before this commit

After this commit

This would be useful for grouping operation.

[liemle3893]

@kevwan Can you please take a look at this PR?

[kevwan]

@kesonan PTAL