List specific config section and its values using the cli

[ephraimbuddy]

This adds an option to list a specific config section with its values through the cli.
e.g for core: airflow config list --section core

(env) ➜  airflow git:(list-section) airflow config list --section database 
[database]
sql_alchemy_conn = sqlite:////Users/ephraimbuddy/airflow/airflow.db
sql_engine_encoding = utf-8
sql_alchemy_pool_enabled = True
sql_alchemy_pool_size = 5
sql_alchemy_max_overflow = 10
sql_alchemy_pool_recycle = 1800
sql_alchemy_pool_pre_ping = True
sql_alchemy_schema = 
load_default_connections = True
max_db_retries = 3

[norm]

Idle thought: I'm wondering if instead of --section database it might be better to have it be an optional positional argument (ie airflow config list and airflow config list database). It feels better to me, but not to the point where I'm advocating for it.

[ephraimbuddy]

Idle thought: I'm wondering if instead of --section database it might be better to have it be an optional positional argument (ie airflow config list and airflow config list database). It feels better to me, but not to the point where I'm advocating for it.

It looks like the --section is more explicit and user-friendly. The optional positional argument looks good too but I feel using --section makes it more explicit

[dstandish]

i agree, i like the keyword. in past, positional args have painted us into a corner.