Add content on deprecating functionality

[ecomodeller]

Problem

The course covers semantic versioning and breaking changes in Module 7, but lacks content on deprecation strategies - a critical skill for package maintainers.

Proposed Content

Add a section to Module 7 (07_packaging.qmd) covering:

1. Deprecation Warnings

• Using Python's warnings module
• Proper stacklevel usage
• DeprecationWarning vs FutureWarning:
  • DeprecationWarning: For developers (filtered by default, shown when running tests)
  • FutureWarning: For end users (always visible, for changes affecting user code)

2. Deprecation Timeline

• Announce in version X.Y
• Remove in version (X+1).0
• Maintain for 1-2 minor releases minimum

3. Communication Strategy

• CHANGELOG updates
• Release notes
• Documentation migration guides
• Clear docstring warnings

4. Code Examples

import warnings

def old_function(x):
    warnings.warn(
        "old_function is deprecated and will be removed in version 2.0. "
        "Use new_function instead.",
        DeprecationWarning,
        stacklevel=2
    )
    return new_function(x)

5. Real-World Examples

Reference deprecation practices from popular packages (pandas, numpy, scikit-learn).

Location

Module 7 - after the "Breaking changes" section (around line 132)