Bucket schema management API?

Proposal:
A BucketSchemaApi to provide convenient access to the bucket schema management features.

Current behavior:

• While it is possible to create an "explicit" Bucket through the Java API, it is not possible to create a bucket schema

Desired behavior:
I want to be able to create a bucket schema for an explicit schema bucket

Alternatives considered:
The only way to do this currently is to directly use the InfluxDb HTTP API. Its quite awkward to be able to access almost all of the InfluxDb features through the client lib, but have to drop down to using a separate HTTP lib and JSON serialization/deserialization lib for my bespoke type for representing bucket schema.

Use case:
Bucket schema seem pretty important for ensuring bucket contents will always fulfill some basic content constraints. An implicit bucket can contain anything, so would require a ton of data validation for even the simplest use-case of bucket content consumption.

首先检查现有的 Java bucket API 和提议的 BucketSchemaApi，然后将它们与 issue 中引用的 InfluxDB HTTP API 进行比较。当客户端可以在不需要单独的 HTTP 或 JSON 库的情况下，为显式 schema 的 bucket 创建 bucket schema 时，即视为完成。