feat: Neo4j backend for popular tables personalization

[joshthoward]

Summary of Changes

Added Neo4j backend implementation for popular tables personalization. Follow on from this PR.

From my previous comments, I would like to do further experimentation on building a real recommender system here, but that doesn't seem to be possible now due to lack of data.

Tests

Test caching on new DB query.

Documentation

N/A

CheckList

Make sure you have checked all steps below to ensure a timely review.

• [-] PR title addresses the issue accurately and concisely. Example: "Updates the version of Flask to v1.0.2"
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.
• [-] PR includes a summary of changes.
• [-] PR adds unit tests, updates existing unit tests, OR documents why no test additions or modifications are needed.
• [-] In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
• [-] PR passes make test

[feng-tao]

@joshthoward could you rebase?

[codecov-io]

Codecov Report

Merging #233 (87e2b44) into master (2752492) will increase coverage by 2.61%.
The diff coverage is 71.15%.

@@            Coverage Diff             @@
##           master     #233      +/-   ##
==========================================
+ Coverage   74.10%   76.72%   +2.61%     
==========================================
  Files          25       27       +2     
  Lines        1255     1336      +81     
  Branches      136      161      +25     
==========================================
+ Hits          930     1025      +95     
+ Misses        297      266      -31     
- Partials       28       45      +17     

Impacted Files	Coverage Δ
metadata_service/api/popular_tables.py	100.00% <ø> (ø)
metadata_service/api/user.py	100.00% <ø> (ø)
metadata_service/proxy/shared.py	28.57% <28.57%> (ø)
metadata_service/api/badge.py	61.29% <61.29%> (ø)
metadata_service/proxy/neo4j_proxy.py	71.65% <61.33%> (-3.35%)	⬇️
metadata_service/proxy/base_proxy.py	67.08% <75.00%> (-0.06%)	⬇️
metadata_service/proxy/atlas_proxy.py	80.34% <79.19%> (-3.97%)	⬇️
metadata_service/__init__.py	76.47% <100.00%> (ø)
metadata_service/api/dashboard.py	81.81% <100.00%> (+8.48%)	⬆️
metadata_service/api/table.py	100.00% <100.00%> (ø)
... and 10 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a7b2ec5...87e2b44. Read the comment docs.

[joshthoward]

@feng-tao the rebase is complete. Sorry that took so long. I didn't see it until now.