Clean-up + Refactorings

[AHReccese]

Reference Issues/PRs

What does this implement/fix? Explain your changes.

In this PR, I apply internal clean-up and refactoring to better cover corner cases, improve robustness.

• Token validation at construction so callers cannot reach the network with empty/invalid credentials.
• Regression tests covering token validation and CWD preservation.
• upload now builds the template package in an isolated temporary directory and restores CWD + cleans up via finally.
• Credentials are passed to twine via subprocess env= instead of mutating os.environ
• pre-existing TWINE_* are stripped to prevent external overrides.
• First subprocess failure is reported as-is (no longer overwritten by next commands).
• Template generators updated to reflect reserver's real Python support (>=3.7, 3.7–3.14).
• Default package metadata in params.py reworked to stop referencing unrelated third-party URLs/emails.
• Test names shortened and explanations moved to inline comments.

Any other comments?

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

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[AHReccese]

Hi Sadra @sadrasabouri,
I tried to add proper comments to explain the changes in the code, feel free to ask any questions you might have.

Best,
AmirH

[codecov]

Codecov Report

❌ Patch coverage is 80.43478% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.66%. Comparing base (d71d7d3) to head (aada650).
⚠️ Report is 142 commits behind head on dev.

Files with missing lines	Patch %	Lines
reserver/uploader.py	79.55%	4 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #129      +/-   ##
==========================================
- Coverage   82.76%   77.66%   -5.10%     
==========================================
  Files           5        6       +1     
  Lines          87      179      +92     
  Branches       10       31      +21     
==========================================
+ Hits           72      139      +67     
- Misses          6       24      +18     
- Partials        9       16       +7     

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[sadrasabouri]

Looks good overall. I only have a minor suggestion.

[sadrasabouri]

Is it actually better to have reserved information for the reserved package? I don't think so.