Set OpenAI Key

[Lucs1590]

This change is related to making life easier for users who do not have their OpenAI key linked to the project, as the documentation indicates. Often, users may not read the documentation and our goal is to make life easier for these users, so that they do not interrupt the execution to be able to define their key and have their detailed analysis, but rather that they have a complete experience so that the application itself makes it easier to use.

Enhancements to functionality:

• Added a new function check_key() to verify if the OPENAI_API_KEY environment variable is set. If not, it prompts the user to enter the key and saves it to a .env file. (src/main.py)
• Updated the main() function to call check_key() before performing LLM analysis. (src/main.py)

Improvements to code readability:

• Modified the download_tcx_file() function to use multi-line string formatting for the URL. (src/main.py)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.67%. Comparing base (bae22bd) to head (bd28ed4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #52      +/-   ##
==========================================
+ Coverage   98.58%   98.67%   +0.09%     
==========================================
  Files           2        2              
  Lines         423      454      +31     
==========================================
+ Hits          417      448      +31     
  Misses          6        6              

Flag	Coverage Δ
unittests	98.67% <100.00%> (+0.09%)	⬆️

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