Make LMDB map size a configurable parameter for nn_ensemble backend.

[mo-fu]

This PR adds the simple solution to close #552, as discussed in the issue.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
3 Code Smells

No Coverage information
0.0% Duplication

[osma]

Great! Can we say this fixes #552 (to auto-close the issue when this is merged)? I think it has to be stated in the opening post to be effective.

[codecov]

Codecov Report

Merging #554 (6313081) into master (ccb9982) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #554   +/-   ##
=======================================
  Coverage   99.49%   99.49%           
=======================================
  Files          80       80           
  Lines        5340     5349    +9     
=======================================
+ Hits         5313     5322    +9     
  Misses         27       27           

Impacted Files	Coverage Δ
annif/backend/nn_ensemble.py	99.25% <100.00%> (-0.01%)	⬇️
tests/test_backend_nn_ensemble.py	100.00% <100.00%> (ø)

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[osma]

LGTM

[osma]

Merged, thanks a lot @mo-fu !

[osma]

As we are nearing the 0.56 release, I added some documentation about this setting to the wiki page of the NN ensemble backend - see this diff for the changes.