Feat/prompt description fix

[AnniePacheco]

Summary

This PR includes the following fixes

• Changed chat_response to be only string and not try it to be compliant to certain schema (textLong)
• Changed source of description to be description from a persona and included in the system prompt
• Fixed a bug, while trying to index a pdf file with more than one page

Changes

• Updated yaml apis/paios/openapi.yaml chat_response type string
• Updated bakend app.py to allow_origins 'http://localhost:3000'
• Updated RagManager change assistant description to be persona description

Related Issues

N/A

Type of Change

New feature (non-breaking change which adds functionality)
Fix past bugs

Checklist

• I have read the CONTRIBUTING documentation.
• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the documentation (if applicable).

Screenshots (if applicable) Example of use:

Additional Context

Tested locally using Swagger.