AIP-38 Add some ids for external tools / integration tests

[pierrejeambrun]

Body

Currently the new UI does not contain any identifier in the DOM to allow external tools (plugins/integration tests framework) to find and manipulates element. Targeting via sibling and child selectors is not reliable.

Some of the major components should have an identifier, we could think of:

• Navigation links
• Toobar (Filters + Searchbar)
• Main content
• Tables, etc...

This should be done for existing code, but a strategy should be in place to know when and how we should add such identifiers during development time.-

Committer

• [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.

[pierrejeambrun]

cc: @vatsrahul1001

[bbovenzi]

@vatsrahul1001 Can you tell me more about where and how we should tag elements for your testing? We should probably put in more data-testids too that we can easily use for unit tests as well.