Add pipeline component examples catalogs for KFP and AA and MLX connector

[ptitzler]

This PR

• adds an example catalog connector for Kubeflow Pipelines
• adds an example catalog connector for Apache Airflow
• adds a catalog connector for the Machine Learning Exchange
• requires Add support Runtime types elyra#2263 RESOLVED
• requires Remove references to schema display_name property elyra#2267 (+ > New undefined shown until merged) RESOLVED
• requires Component catalogs schemaspace elyra#2282 RESOLVED
• adds a catalog connector directory
• adds a build-your-own-connector stub
• updates the repository README with links to the connector content

Add examples catalog user experience (Airflow shown):

• Open "Manage Components"

• Add catalog (+)

• New Apache Airflow example components catalog

• Enter a catalog name (any string) - all other inputs are pre-populated.
  

  Note that the Learn more... link opens the connector's GitHub repository README, which contains information about the connector. (For built-in catalog types the link opens the pipeline components topic in the user guide, which introduces catalogs.)

• Expand palette in VPE
  

Note that the following information is persisted for each node in the .pipeline file (irrelevant information was removed from the KFP snippet below):

"type": "execution_node",
"op": "elyra-kfp-examples-catalog:737915b826e9",
"component_description": "Filter input text according to the given regex pattern using shell and grep.",
"component_source": "{'catalog_type': 'elyra-kfp-examples-catalog', 'component_ref': {'component-id': 'filter_text_using_shell_and_grep.yaml'}}",

Airflow:

"type": "execution_node",
"op": "elyra-airflow-examples-catalog:3a55d015ea96",
"component_source": "{'catalog_type': 'elyra-airflow-examples-catalog', 'component_ref': {'component-id': 'bash_operator.py'}}",

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[lresende]

Please make sure to update LICENSE files accordingly to mention new files as in PR 2272

[kiersten-stokes]

This is working great! I installed from source for my tests

[ptitzler]

A couple pending changes:

• split connector into two connectors (one for kfp, one for airflow):
  • avoids issues like the ones we are facing with other BYOs (stuff that doesn't belong together is stored together) -> this will make it easier for somebody to create an "examples" connector for another runtime type
  • customized schema, which pre-populates as much as possible, e.g. for KFP
  • add connector
  • 
  • followed by "enable connector"
  • 

Note:

• the elyra setup.py will list both connectors as extras
• the Dockerfile templates we include in the elyra repo will install [the relevant] connector package(s) AND invoke elyra-metadata install .... This way the example components are available in the VPE palette by default. Since these are just templates, customers can choose to remove the dependencies/setup steps in their customized version if they want to exclude the example components (or use their own "forked" examples instead.

[kevin-bates]

The updates sound great. I still think it would be good to expose a filter/regex schema property that can be applied so users can build connector instances that are subsets of the complete set.

[ptitzler]

Please make sure to update LICENSE files accordingly to mention new files as in PR 2272

Thank you, I have totally missed that. I added a license file to the Kubeflow Pipelines connector's resources directory. The Airflow components already have their own license embedded, so we should be good there!

[kevin-bates]

Sorry - I just noticed my comments were applied to a specific commit, which requires you to have to open the commit link to get their context. What a hassle - I apologize.

[kevin-bates]

Aside from the circular ref comment below, the connector schemas should include the following updates (can't apply in-line commenting so adding here):

• The $id values still reflect the combined form of the repo
• The display_name property should be removed as it's redundant with title. (This comment is NOT apply to the display_name property definition down in the properties stanza - which applies to instances.) All schemas are being updated in this manner in Remove references to schema display_name property elyra#2267
• The schemaspace and schemaspace_id values should be updated to component-catalogs and 8dc89ca3-4b90-41fd-adb9-9510ad346620, respectively once Component catalogs schemaspace elyra#2282 is merged.

[ptitzler]

[...] the connector schemas should include the following updates (can't apply in-line commenting so adding here):

• The $id values still reflect the combined form of the repo

Fixed in both schemas!

• The display_name property should be removed as it's redundant with title. (This comment is NOT apply to the display_name property definition down in the properties stanza - which applies to instances.) All schemas are being updated in this manner in elyra-ai/elyra#2267

Removed the top level display_name property from both schemas!

• The schemaspace and schemaspace_id values should be updated to component-catalogs and 8dc89ca3-4b90-41fd-adb9-9510ad346620, respectively once elyra-ai/elyra#2282 is merged.

Adding this to the TODO list

[kiersten-stokes]

LGTM! I incorporated the changes that this PR is dependent on and tested all three catalog types -- all are working great

[ptitzler]

• chemaspace and schemaspace_id values should be updated to component-catalogs and 8dc89ca3-4b90-41fd-adb9-9510ad346620, respectively once elyra-ai/elyra#2282 is merged.

Done!

[ptitzler]

@akchinSTC @lresende @kevin-bates @kiersten-stokes you should have received pending collaborator invitations for three packages from PyPI

[ptitzler]

For test purposes version 0.0.1 of each package was published to unblock elyra-ai/elyra#2286. Once development has completed and no issues were found version 0.0.1 will be replaced by 0.1.0.