Add Storage Policy for Computed KnowledgeSources

[Supereg]

Add Storage Policy for Computed KnowledgeSources

♻️ Current situation & Problem

Currently, all instances of ComputedKnowledgeSource are getting cached. Meaning, the result of the compute method is stored in the SharedRepository and each retrieval will first check if there is a value present before calling compute.
This reduces the control a ComputedKnowledgeSource has on how its value is dynamically computed.
This also has the primary drawback that the respective subscript has to be mutating get.

💡 Proposed solution

This PR introduces the concept of a StoragePolicy for ComputedKnowledgeSources. By default it is set to Store but may be adjusted to AlwaysCompute. Respective subscripts were added to provide the expected implementation.

⚙️ Release Notes

• Addes Storage Policy for Computed KnowledgeSources

➕ Additional Information

Note: This PR is currently still based of the 0.6.0 release.

Related PRs

• Rethought Account Service Model with reimagined Account Setup and new Account Overview SpeziAccount#7 is based on this as it's computed E-Mail AccountValue depends on either having set a value in the shared repository or using the userId if the userId is an email address. This should not be cached, to dynamically reflect changes of the userId AccountValue.

Testing

Additionally test vectors were added.

Reviewer Nudging

Look the the newly defined protocols and protocol extensions, as well as the updated SharedRepository implementation.

Code of Conduct & Contributing Guidelines

By submitting creating this pull request, you agree to follow our Code of Conduct and Contributing Guidelines:

• I agree to follow the Code of Conduct and Contributing Guidelines.

[codecov]

Codecov Report

Merging #75 (885d706) into main (c98b2e5) will increase coverage by 2.02%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #75      +/-   ##
==========================================
+ Coverage   95.50%   97.52%   +2.02%     
==========================================
  Files          34       34              
  Lines         600      604       +4     
==========================================
+ Hits          573      589      +16     
+ Misses         27       15      -12     

Files Changed	Coverage Δ
Sources/Spezi/Spezi/SpeziLogger.swift	100.00% <ø> (ø)
...edRepository/KnowledgeSource/KnowledgeSource.swift	100.00% <100.00%> (ø)
...rces/Spezi/SharedRepository/SharedRepository.swift	100.00% <100.00%> (+37.50%)	⬆️

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[PSchmiedmayer]

Thank you @Supereg, looks great!