fix: login button does not render

[villebro]

SUMMARY

PR #19051 caused a regression causing the welcome page to fail to render for anonymous users. This adds a new type UndefinedUser (an empty object), adds type guards for both User and UserWithPermissionsAndRoles and updates related functions based on the following comment:

superset/superset-frontend/src/dashboard/util/findPermission.test.ts

Lines 137 to 138 in 6e8e29c

	// in redux, when there is no user, the user is actually set to an empty object,
	// so we need to handle missing roles as well as a missing user.s

In addition, tests are added to ensure isAdminUser works for all relevant user types.

AFTER

Now the welcome page renders correctly:

BEFORE

When going to the main page without being logged in, the following appears:

TESTING INSTRUCTIONS

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 #19685 (b6d5b04) into master (6e8e29c) will decrease coverage by 0.00%.
The diff coverage is 88.88%.

❗ Current head b6d5b04 differs from pull request most recent head 0a24c83. Consider uploading reports for the commit 0a24c83 to get more accurate results

@@            Coverage Diff             @@
##           master   #19685      +/-   ##
==========================================
- Coverage   66.50%   66.50%   -0.01%     
==========================================
  Files        1683     1684       +1     
  Lines       64520    64525       +5     
  Branches     6607     6612       +5     
==========================================
+ Hits        42910    42913       +3     
  Misses      19916    19916              
- Partials     1694     1696       +2     

Flag	Coverage Δ
javascript	51.12% <88.88%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...rset-frontend/src/dashboard/util/findPermission.ts	92.30% <85.71%> (-7.70%)	⬇️
superset-frontend/src/types/bootstrapTypes.ts	100.00% <100.00%> (ø)
...perset-frontend/src/views/components/MenuRight.tsx	66.66% <0.00%> (-1.15%)	⬇️

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[kgabryje]

Tested, LGTM. Thanks for the fix!

[sadpandajoe]

🏷️ preset:2022.15