[feature-request] sink to cloud storage: customized delimiter with 2 characters

[zhangjinpeng87]

Is your feature request related to a problem?

TiCDC has a one character limitation for CSV delimiter, this will limit users using special characters like hex(FF, FE) as delimiter.

Describe the feature you'd like

When user specify the delimiter, supports at most 2 characters delimiter.

Describe alternatives you've considered

There is a hard limitation that the delimiter is 1 character, so there is no alternative to workaround this problem.

Teachability, Documentation, Adoption, Migration Strategy

This is an extension for existing sink to CSV capability, this will give users better capability to customize their CSV format.

[lidezhu]

Some customers use separator like |@| in their env. So we need to relief the restriction further to support 3 characters.