[FLINK-38839][runtime] Support semicolon delimiter for table-options

[tchivs]

Summary

Allow table-options in transform rules to use semicolon ; as the key/value pair delimiter so option values can safely contain commas (e.g. sequence.field=gxsj,jjsj). Keep comma delimiter for backward compatibility.

Motivation

Some downstream table options are multi-value and use comma inside the value. The existing key1=value1,key2=value2 syntax makes those options impossible to express reliably.

Changes

• SchemaMetadataTransform parses table-options pairs using:
  • ; when present in the string, otherwise ,
  • split("=", 2) to avoid breaking values containing =
• Docs updated to mention semicolon delimiter for comma-in-value cases.
• New unit tests for the parsing behavior.

Behavior

• Still supports legacy format:
  • table-options: key1=value1,key2=value2
• Supports semicolon format (recommended when values contain commas):
  • table-options: sequence.field=gxsj,jjsj;file-index.range-bitmap.columns=jjsj;file-index.bloom-filter.columns=jjdbh
• Note: delimiter is chosen by presence of ; (do not mix , and ; in the same string).

[tchivs]

Thanks for the suggestion @leonardBang! I've updated the PR to support custom delimiters as you recommended.

Changes made:

1. Added a new optional configuration table-options.delimiter that allows users to specify any custom delimiter (e.g., ;, |, $, etc.)
2. The default value is , for backward compatibility
3. Updated documentation with examples showing how to use custom delimiters

Example usage:

transform:
  - source-table: mydb.mytable
    table-options: sequence.field=gxsj,jjsj;file-index.bloom-filter.columns=jjdbh
    table-options.delimiter: ";"

This approach is more flexible and powerful as users can now choose any delimiter that suits their needs.