fix: add validation to the profile if the prompt_template does not exist

[efortish]

related issue: #89 (comment)

Validate prompt_template existence in AIWorkflowProfile

Description

Prompt templates can be referenced by slug or UUID in workflow profiles, but there was no validation checking if the referenced template actually exists in the database. This caused silent failures at runtime — the system would fall back to inline prompts or send no custom prompt to the LLM without any warning.

Changes

• template_utils.py: Added _validate_prompt_templates() function that iterates over all processors in processor_config, checks for prompt_template fields, and verifies they exist in the DB via PromptTemplate.load_prompt(). Integrated into the existing _validate_semantics() pipeline.
• admin.py: Added clean() method to AIWorkflowProfileAdminForm that builds the effective config (base template + patch) and runs validate_workflow_config(). Invalid prompt templates now block saving in Django Admin with a descriptive error message.

Tests

Added TestValidatePromptTemplates covering: existing slug/UUID, nonexistent slug/UUID, multiple processors, mixed valid/invalid, empty/null values, and Admin form integration

[openedx-webhooks]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.98%. Comparing base (e6caf77) to head (e0885c4).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
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+ Coverage   90.74%   90.98%   +0.23%     
==========================================
  Files          48       48              
  Lines        4389     4504     +115     
  Branches      271      277       +6     
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+ Hits         3983     4098     +115     
  Misses        317      317              
  Partials       89       89              

Flag	Coverage Δ
unittests	90.98% <ø> (+0.23%)	⬆️

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[felipemontoya]

Thanks @efortish. The PR does exactly what it says. The code is well tested and will solve this issue.

It could still happen that an existing prompt_template is deleted and the profile becomes invalid silently. I think this is acceptable for now (same pattern as ForeignKey without CASCADE), but worth remembering as a known limitation. I'll merge this now, but If you want to document that feel free to open a new PR.