fix: add alert report timeout limits

[riahk]

SUMMARY

• Working Timeout and Grace Period fields should not be negative
• Adds min value to modal input fields to prevent user from setting negative values

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

Manual Test:

1. Open alert/report modal
2. Enter values for Working Timeout/Grace Period (where applicable)
3. Confirm that value cannot be set below 0

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

[codecov-io]

Codecov Report

Merging #12926 (67a56d8) into master (2ce7982) will increase coverage by 13.72%.
The diff coverage is 51.42%.

@@             Coverage Diff             @@
##           master   #12926       +/-   ##
===========================================
+ Coverage   53.06%   66.78%   +13.72%     
===========================================
  Files         489      493        +4     
  Lines       17314    29084    +11770     
  Branches     4482        0     -4482     
===========================================
+ Hits         9187    19425    +10238     
- Misses       8127     9659     +1532     

Flag	Coverage Δ
cypress	?
python	66.78% <51.42%> (?)

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

Impacted Files	Coverage Δ
superset/constants.py	100.00% <ø> (ø)
superset/examples/birth_names.py	73.19% <ø> (ø)
...43f2fdb_add_granularity_to_charts_where_missing.py	0.00% <0.00%> (ø)
...s/260bf0649a77_migrate_x_dateunit_in_time_range.py	0.00% <0.00%> (ø)
...ons/versions/41ce8799acc3_rename_pie_label_type.py	0.00% <0.00%> (ø)
superset/connectors/sqla/views.py	62.43% <4.34%> (ø)
superset/views/datasource.py	88.70% <16.66%> (ø)
superset/viz.py	58.61% <27.27%> (ø)
superset/views/core.py	72.91% <71.42%> (ø)
superset/charts/commands/exceptions.py	92.85% <77.77%> (ø)
... and 925 more

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[dpgaspar]

I think it makes sense to add a validation on the backend also:
https://github.com/apache/superset/blob/master/superset/reports/schemas.py#L162

fields.Integer(validate=[Range(min=1, error="Value must be greater than 0")])

[willbarrett]

Let's also add a test for this change.

[amitmiran137]

Looks good.
Do we enforce this on the BE as well?

[willbarrett]

One comment on the python. Let's add some tests for the back-end validations as well.

[willbarrett]

I'm not sure if this is correct, as reports do not require a grace period.

[riahk]

I may be mistaken, but I'm pretty sure we use this schema for both alerts and reports.