[Feature][function] 是否考虑支持自定义函数

[gaopan-05]

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• [X] I had searched in the issues and found no similar feature requirement.

Description

支持用户上传自定义函数jar包，并在 flinksql 中使用

Use case

No response

Related issues

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Are you willing to submit a PR?

• [X] Yes I am willing to submit a PR!

Code of Conduct

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[wmtbnbo]

It supports function customization，The development method can refer to the flink official documents,Put the expansion package under directory plugins/.Use the following method to load functions in the SQL file： create function TO_CHAR AS 'com.haier.sql.udf.ToCharFunction';

[Zzm0809]

#1153

[Zzm0809]

#1144

[Zzm0809]

#1137