fix: Schema is not retaining the correct column order

[mjsqu]

Fixes #62 by refactoring the desired_columns function to use lists instead of sets as they preserve order. List comprehensions are used to filter the lists rather than a loop. Operations such as intersection, difference and union are also replaced with list comprehensions.

Also includes modifications to the existing TestSelectsAppropriateColumns:

• Adds more columns to strengthen proof that ordering is preserved
• Assertion changed to compare two lists, will fail if they are not in the same order
• Added a duplicate column to the select list

Adds new test TestInvalidInclusion which tests that an exception is raised when an inclusion value of "invalid" is supplied, which is not one of the valid values:

• automatic
• available
• unsupported

[mjsqu]

For my own future reference, I could have more quickly run my updated tests by doing:

poetry install
poetry run pytest tests/test_tap_mssql.py -k TestSelects -v
poetry run pytest tests/test_tap_mssql.py -k TestInvalid -v

Running all tests requires the build of a database (as supplied by the docker image in the tox.ini) - but the functionality I was testing didn't require a connection to SQL Server.

[s7clarke10]

Hi @mjsqu ,

I have reviewed the changes and like what you have done - thank you 🥇 .

My testing included.

1. Peer Review of the code
2. Compare the discovery of the schema (current vs PR)
3. Compare the column ordering of loaded data in target-snowflake (current vs PR)
4. Compare the content diff of result in target-snowflake (current vs PR).

All passed successfully.

Could we add the following changes however.

1. Update the .bumpversion.cfg with new version
2. Update the pyproject.toml with new version
3. Update the CHANGELOG.md with description of latest version / change.
4. Rebuild the pyproject lockfile 👍

   poetry lock --no-update

Thank you.

[mjsqu]

These are done:

• Update the .bumpversion.cfg with new version
• Update the pyproject.toml with new version
• Update the CHANGELOG.md with description of latest version / change.

I ran poetry lock --no-update but there are no changes as I have made no updates to dependencies

[s7clarke10]

Thank you for adding the version updates. Change approved. Thank you.