feat(dashboard_rbac): dashboards API support for roles create/update + roles validation

[amitmiran137]

SUMMARY

the needed support for managing roles via v1 API to be used from the UI and for app 2 app calls
resolves #10408

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[amitmiran137]

@ktmud @villebro Could you review?

[villebro]

A few comments

[codecov-io]

Codecov Report

Merging #12865 (9400161) into master (9a7fba8) will decrease coverage by 3.33%.
The diff coverage is 90.19%.

@@            Coverage Diff             @@
##           master   #12865      +/-   ##
==========================================
- Coverage   67.04%   63.71%   -3.34%     
==========================================
  Files        1022      490     -532     
  Lines       50186    30271   -19915     
  Branches     5204        0    -5204     
==========================================
- Hits        33647    19287   -14360     
+ Misses      16404    10984    -5420     
+ Partials      135        0     -135     

Flag	Coverage Δ
cypress	?
javascript	?
python	63.71% <90.19%> (-0.38%)	⬇️

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

Impacted Files	Coverage Δ
superset/dashboards/api.py	86.63% <ø> (ø)
superset/dashboards/commands/update.py	83.07% <70.58%> (-5.61%)	⬇️
superset/commands/exceptions.py	92.00% <100.00%> (+0.69%)	⬆️
superset/commands/utils.py	100.00% <100.00%> (ø)
superset/dashboards/commands/create.py	93.87% <100.00%> (+1.56%)	⬆️
superset/dashboards/schemas.py	98.83% <100.00%> (+0.04%)	⬆️
superset/security/manager.py	91.07% <100.00%> (+0.05%)	⬆️
superset/db_engines/hive.py	0.00% <0.00%> (-85.72%)	⬇️
superset/sql_validators/postgres.py	50.00% <0.00%> (-50.00%)	⬇️
superset/db_engine_specs/hive.py	73.84% <0.00%> (-17.31%)	⬇️
... and 557 more

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[ktmud]

LGTM with one tiny tiny nit