fix: Revert back to straightforward PromptBuilder

[vblagoje]

Why:

This Pull Request reverts the PromptBuilder class back to its more straightforward implementation before attempts to use it for both chat and non-chat messages. With the introduction of DynamicPromptBuilder, the original PromptBuilder will serve static prompt use cases. We'll subsequently see if it makes sense to adapt PromptBuilder to support chat-based prompting.

What:

The PR includes the following changes:

• Removal of the capability to use dynamic templates based on template variables. The PromptBuilder will no longer support different templates for each message or dynamic templating on a per-user message basis.
• Simplification of the PromptBuilder class. It now solely focuses on rendering a prompt from a Jinja2 template string. The input types for the component are strictly the template variables found in the template string.
• Removal of several functionalities including handling of ChatMessage data class, conditional template rendering based on user messages, and error checks related to the presence of either template string or template variables.
• The constructor of PromptBuilder is now simplified to accept only a template string and no longer supports the option of providing template variables separately.

How can it be used:

After this change, PromptBuilder will be used for static templating scenarios where a single, consistent template string is required throughout the component's lifetime. This can be useful in applications where dynamic templating is unnecessary and a straightforward, consistent, prompt structure is preferred.

How did you test it:

Testing should focus on ensuring that the PromptBuilder correctly renders prompts using the provided Jinja2 template string. Tests for chat-based prompting were also reverted.

Notes for the reviewer:

• See changes

[masci]

LGTM!