Feature/selectable middleware

[teemukataja]

Background

We have use cases at CSC where we are using sda-download in three different contexts, and each of them have a different authentication middleware. We have been maintaining three separate implementations, and would now like to streamline them into a single codebase. These changes here would lay the foundation for the capabilities we need (changing middleware, more versatile cache), and then we would implement our needs in our private repository.

Changes

• new config app.middleware, with a default value default
• TokenMiddleware is now the default middleware, custom middlewares can be built in the middleware package, and be selected for runtime using the config (added a readme to the middleware directory for instructions)
• session cache now works with the whole cache struct instead of only the datasets slice, so that it can be used to store more items
• no breaking changes, only refactoring to allow us to use the same codebase for more use cases! 😄

[pontus]

Looks OK.

Could possibly have a short explainer in middleware.go to clarify the cache flow (at least I got tripped up a few times thinking about it), but I'm fine with merging as is.

[teemukataja]

Looks OK.

Could possibly have a short explainer in middleware.go to clarify the cache flow (at least I got tripped up a few times thinking about it), but I'm fine with merging as is.

I agree, I'll see if I can refactor it a little bit after this PR to simplify it

[codecov-commenter]

Codecov Report

Merging #295 (6f21386) into main (c14131c) will decrease coverage by 0.11%.
Report is 16 commits behind head on main.
The diff coverage is 88.23%.

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@@            Coverage Diff             @@
##             main     #295      +/-   ##
==========================================
- Coverage   67.45%   67.34%   -0.11%     
==========================================
  Files          10       10              
  Lines        1598     1611      +13     
==========================================
+ Hits         1078     1085       +7     
- Misses        484      489       +5     
- Partials       36       37       +1     

Flag	Coverage Δ
unittests	67.34% <88.23%> (-0.11%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
internal/config/config.go	58.36% <14.28%> (-1.37%)	⬇️
api/api.go	93.18% <100.00%> (+0.32%)	⬆️
api/middleware/middleware.go	100.00% <100.00%> (ø)
api/s3/s3.go	62.22% <100.00%> (+0.64%)	⬆️
api/sda/sda.go	85.78% <100.00%> (ø)
internal/session/session.go	91.22% <100.00%> (-0.71%)	⬇️

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