docs: Update Airflow next steps to indicate Python version support

[EMCP]

Meltano Version

2.3.0

Python Version

3.10

Bug scope

CLI (options, error messages, logging, etc.)

Operating System

Kubuntu 22.04

Description

while attempting to install .. got stuck when attempting to add airflow will put replication steps here

1. start a blank new project with the latest meltano available..

$ meltano discover orchestrators
2022-07-30T18:38:08.881040Z [info     ] Environment 'dev' is active
Orchestrators
airflow

$ meltano add orchestrators airflow
2022-07-30T18:38:18.506731Z [info     ] Environment 'dev' is active
Added orchestrator 'airflow' to your Meltano project
Variant:        apache (default)
Repository:     https://github.com/apache/airflow
Documentation:  https://docs.meltano.com/guide/orchestration

Added required file bundle 'files-airflow' to your Meltano project
Variant:        meltano (default)
Repository:     https://github.com/meltano/files-airflow
Documentation:  https://hub.meltano.com/files/files-airflow

Installing orchestrator 'airflow'...
Installing file bundle 'files-airflow'...
Orchestrator 'airflow' could not be installed: failed to install plugin 'airflow'.
ERROR: 404 Client Error: Not Found for url: https://raw.githubusercontent.com/apache/airflow/constraints-2.1.2/constraints-3.10.txt

Installed file bundle 'files-airflow'
Adding 'files-airflow' files to project...
Created orchestrate/dags/meltano.py
Installed 1/2 plugins
Failed to install plugin(s)

this might be a hinderance to meltano fully supporting 3.10 at this time.. I understand though and will back off to 3.9 or lower

Code

No response

[EMCP]

seems according to apache/airflow#19059 , support for py 3.10 will come in v2.3.0 of airflow

[EMCP]

can confirm .. https://raw.githubusercontent.com/apache/airflow/constraints-2.3.0/constraints-3.10.txt is a valid path

is there a troubleshooting area I can add this tip to? or how can I help smooth this out for future users?

  orchestrators:
  - name: airflow
    variant: apache
    pip_url: apache-airflow==2.3.0 --constraint https://raw.githubusercontent.com/apache/airflow/constraints-2.3.0/constraints-${MELTANO__PYTHON_VERSION}.txt

[tayloramurphy]

@EMCP this makes me think of this issue #126

Related to this too, we have an issue to get Airflow upgraded to 2.3 #658 but there's some work in Meltano we'd need to do to make that happen.

That said, we could add a note in the next_steps in https://github.com/meltano/hub/blob/main/_data/meltano/orchestrators/airflow/apache.yml#L20 to alert users to the Python/Airflow mismatch.