Fix identification of invalid objects with stac_version field

[duckontheweb]

Related Issue(s): #

• Exception if Catalog doesn't have a description field during catalog.get_children() #464 (see this comment)

Description:

Objects with stac_version == 1.0.0 but without a type field were being incorrectly identified by pystac.serialization.identify_stac_object_type as Catalogs. This fixes that method to return None in that case (indicating a dict that does not represent a valid STAC object).

Also adds the "type" field to Catalogs and Collections during migration.

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[duckontheweb]

cc: @philvarner

[codecov-commenter]

Codecov Report

Merging #487 (0a81994) into main (f9573f8) will increase coverage by 0.00%.
The diff coverage is 95.23%.

@@           Coverage Diff           @@
##             main     #487   +/-   ##
=======================================
  Coverage   91.66%   91.66%           
=======================================
  Files          40       40           
  Lines        5245     5258   +13     
=======================================
+ Hits         4808     4820   +12     
- Misses        437      438    +1     

Impacted Files	Coverage Δ
pystac/serialization/identify.py	92.95% <94.73%> (-0.02%)	⬇️
pystac/serialization/migrate.py	87.09% <100.00%> (-0.21%)	⬇️

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