docs: add license headers

[afuetterer]

Description

This PR adds a new pre-commit hook, that adds this license headers to each python module:

# SPDX-FileCopyrightText: 2020 PANGAEA (https://www.pangaea.de/)

# SPDX-License-Identifier: MIT

This should be sufficient, no need to copy the whole MIT license text into a module.

Two things I am unsure about:

• the copyright years though. You want to change those to the year the module was created, e.g. 2021, 2022, etc?
• the copyright text could potentially include the list of authors per module

What do you think?

Types of changes

• Build related changes
• Documentation content changes

Checklist

• I have read the contributor guide.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[github-actions]

📋 Pytest Results

18 tests  ±0   18 ✅ ±0   25s ⏱️ +4s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 63669a8. ± Comparison against base commit c7cb7e5.

♻️ This comment has been updated with latest results.

[huberrob]

A good one! I think the year should be kept but it should be the year, the file has been created. But since within the EU copyright is valid 70 years after creation and the creation year is clearly visible at Githuib, we could also just leave it away..

[afuetterer]

Fixed the merge conflict.

[afuetterer]

You can decide on this one.

This hook will add the license header when you commit a new python module.

[github-actions]

📋 Code Coverage

Package	Line Rate	Branch Rate	Health
.	51%	35%	➖
config	100%	100%	✔
controllers	85%	56%	✔
evaluators	64%	37%	➖
harvester	63%	52%	➖
helper	66%	55%	➖
models	80%	87%	✔
Summary	70% (6633 / 9461)	60% (2815 / 4672)	➖