MAINT: linkahead rename

Summary

• in User Documentation (online, readmes, other doc folders)
• depricate old imports
• add new ways to import
• search and replace in remaining files; change only if it has no functional implications

Test Environment

pipelines

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
  • How do I develop or debug the software? Assume novice developers.
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.

README_SETUP.md

@@ -68,3 +68,9 @@ Build documentation in `build/` with `make doc`.
 - [Google Style Python Docstrings](https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html)
 - [Google Style Python Docstrings 2nd reference](https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings)
 - [References to other documentation](https://www.sphinx-doc.org/en/master/usage/extensions/intersphinx.html#role-external)
+
+## Migration ##
+
+### From xxx to xxx ###
+
+- `.linkaheadignore`