Add new admin option to customize terms of use for file download

[SamuelWei]

Implements #1435

Type (Highlight the corresponding type)

• Bugfix
• Feature
• Documentation
• Refactoring (e.g. Style updates, Test implementation, etc.)
• Other (please describe):

Checklist

• [x] Code updated to current develop branch head
• [x] Passes CI checks
• [x] Is a part of an issue
• [x] Tests added for the bugfix or newly implemented feature, describe below why if not
• [x] Changelog is updated
• [x] Documentation of code and features exists

Changes

• Add new admin option to customize terms of use for file download

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.35%. Comparing base (df88958) to head (9c44431). Report is 19 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1440 +/- ## ============================================= + Coverage 95.32% 95.35% +0.02% Complexity 1323 1323 ============================================= Files 203 203 Lines 4579 4583 +4 ============================================= + Hits 4365 4370 +5 + Misses 214 213 -1 ```

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[cypress[bot]]

PILOS    Run #809

Run Properties:   Passed #809  •  e54af954ef: Add new admin option to customize terms of use for file download (#1440)

Project	PILOS
Run status	Passed #809
Run duration	03m 01s
Commit	e54af954ef: Add new admin option to customize terms of use for file download (#1440)
Committer	Samuel Weirich
View all properties for this run ↗︎

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Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	46