Feature: Add Placeholder Support for .chain Files with Dialog Mode and YAML References

[PatrickDiallo23]

Enhance the .chain file format to include placeholders that prompt the user for values during execution. The filled placeholders will generate updated .chain files and corresponding YAML files for reuse.

Example Workflow:

1. Input .chain file with placeholders:

Implement an application that collects use [[date_to_collect|what data do you want to collect?]] and saves it in [[file|file name]].[[format|format type?]]
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Cover it with tests 
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Add the possibility to access this service via the REST endpoint
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Add REST endpoint which returns [[file]].csv as the JSON

2. Dialog prompts user:

• "What data do you want to collect?" → User, Email.
• "File name?" → user_data.
• "Format type?" → csv.

3. Generate updated .chain and YAML files with resolved values.

Related to #16.