StTemplateRenderer delimiter token allows multiple characters

[johnyannj]

Please do a quick search on GitHub issues first, the feature you are about to request might have already been requested.

Expected Behavior

StTemplateRenderer.builder().startDelimiterToken(“{{”).endDelimiterToken("}}").build()

Current Behavior

StTemplateRenderer.builder().startDelimiterToken('{').endDelimiterToken('}').build()

Context

Single Char is easy conflict with normal content in prompt.

[zjxzjw]

Submitted PR, please refer to review #3801

[ilayaperumalg]

@zjxzjw Thanks for the report. @zjxzjw Thanks for the PR!