feat: Adds a key-value endpoint to store charts form data

[michael-s-molina]

SUMMARY

Currently, the Explore state is being stored in the URL to allow users to preserve their current interactions in case of a refresh and also to transfer context between the dashboard and Explore. The problem with this approach is that when the size of the state is big, it provokes URL length problems with the major browsers.

The proposed solution in this PR is to store the Explore state on the server-side and keep in the URL only a secure key that gives access to the stored content. To do that, we'll extend the current chart endpoint with an additional path that supports the storage of information in the form of key-value entries. By making this endpoint relative to the main resource we can reuse the security model and access grants.

The additional endpoint and the supported operations are:

POST api/v1/chart/<id>/form_data

BODY 
{
   // Any type of JSON supported text.
   value: <string>,
}

RESPONSE
{
   // The key generated on the server-side
   key: <string>
}

PUT api/v1/chart/<id>/form_data/<key>

BODY
{
   // Any type of JSON supported text.
   value: <string>,
}

RESPONSE
{
   // The result of the operation
   message: <string>
}

GET api/v1/chart/<id>/form_data/<key>

RESPONSE
{
   // Any type of JSON supported text.
   value: <string>,
}

DELETE api/v1/chart/<id>/form_data/<key>

RESPONSE
{
   // The result of the operation
   message: <string>
}

All the endpoints accept an optional query parameter called dataset_id that is used for the cases when a chart is not saved yet but we want to preserve the state. In this case, the chart ID shall be set to 0:

POST api/v1/chart/0/form_data?dataset_id=<id>

The keys are generated on the server-side using the https://docs.python.org/3/library/secrets.html#secrets.token_urlsafe function and the value can be any JSON supported text.

To store the key-value entries, this PR uses Flask-Caching, which enables support to different backends like Redis, Memcached, file system, etc. It also allows the configuration of expiration times for the stored entries in order to discard the ones that are not being used anymore and optimize the required storage space.

This PR also allows a configuration to preserve actively accessed entries by renewing the expiration time every time a value is retrieved.

TESTING INSTRUCTIONS

1 - Execute Python tests
2 - All tests should pass

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #17882 (fca7ace) into master (3a9bd12) will decrease coverage by 0.38%.
The diff coverage is 98.28%.

@@            Coverage Diff             @@
##           master   #17882      +/-   ##
==========================================
- Coverage   67.10%   66.71%   -0.39%     
==========================================
  Files        1612     1627      +15     
  Lines       64999    65428     +429     
  Branches     6872     6872              
==========================================
+ Hits        43616    43653      +37     
- Misses      19513    19905     +392     
  Partials     1870     1870              

Flag	Coverage Δ
hive	52.15% <50.34%> (-1.17%)	⬇️
mysql	81.17% <98.28%> (-1.05%)	⬇️
postgres	81.22% <98.28%> (-1.05%)	⬇️
presto	52.00% <50.34%> (-1.16%)	⬇️
python	81.66% <98.28%> (-1.05%)	⬇️
sqlite	80.91% <98.28%> (-1.04%)	⬇️

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

Impacted Files	Coverage Δ
superset/key_value/commands/entry.py	100.00% <ø> (ø)
superset/charts/form_data/commands/update.py	90.90% <90.90%> (ø)
superset/charts/form_data/commands/create.py	94.11% <94.11%> (ø)
superset/charts/form_data/commands/delete.py	94.73% <94.73%> (ø)
superset/charts/form_data/commands/get.py	95.65% <95.65%> (ø)
superset/charts/commands/exceptions.py	91.48% <100.00%> (+0.37%)	⬆️
superset/charts/form_data/api.py	100.00% <100.00%> (ø)
superset/charts/form_data/utils.py	100.00% <100.00%> (ø)
superset/config.py	91.74% <100.00%> (+0.10%)	⬆️
superset/dashboards/filter_state/api.py	100.00% <100.00%> (ø)
... and 69 more

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[villebro]

First pass comments. The new API design looks good, but I think we may still need some further fine tuning.

[michael-s-molina]

First pass comments. The new API design looks good, but I think we may still need some further fine tuning.

Great comments @villebro. I tackled them all.

[villebro]

A few last comments, but looking really good 👍 LMKWYT

[villebro]

Approving to unblock this PR as the majority of my comments were not blocking.

[michael-s-molina]

Thank you reviewers for your great contributions. I will continue the work on the client-side now, where further adjustments can be made.