Portfolio optimization - plot, show and load endpoints

[montezdesousa]

Description

Fixes #3362
Fixes #3361
Fixes #3360

• Reviewed optimization docstrings
• Adds examples in docstrings, some still missing

• Summary of the change / bug fix.
• Link # issue, if applicable.
• Screenshot of the feature or the bug before/after fix, if applicable.
• Relevant motivation and context.
• List any dependencies that are required for this change.

How has this been tested?

• Please describe the tests that you ran to verify your changes.
• Provide instructions so we can reproduce.
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• Make sure affected commands still run in terminal
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Checklist:

• Update our Hugo documentation following these guidelines.
• Update our tests following these guidelines.
• Make sure you are following our CONTRIBUTING guidelines.
• If a feature was added make sure to add it to the corresponding scripts file.

Others

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.

[Chavithra]

Looks ok to me.