Add logging function to allow for remote app-hosting debugging

[joshhalley]

Utilize app-hosting RESTCONF call for function generation.

[joshhalley]

I checked this out, the RPC logic is pretty limited when it comes to the generation of useful log messages over RESTCONF:

curl -X POST -u <username>:<password> 'https://192.0.2.24/restconf/operations/Cisco-IOS-XE-logging-ios-actions-rpc:send-log' --insecure -H "Content-Type: application/yang-data+json" -H "Accept: application/yang-data+json" -d '{ "Cisco-IOS-XE-logging-ios-actions-rpc:input": { "message": "Informational test log", "severity": 1 } }'

It results in the log line seen at 20:27:38.625, but then is closely followed by two other messages.

cat8kv-01#
*Jan 26 20:27:38.625: %SYS-1-USERLOG_ALERT: Message from tty0(user id: ): Informational test log
*Jan 26 20:27:38.593: %DMI-5-AUTH_PASSED: R0/0: dmiauthd: User '<username>' authenticated successfully from 10.42.0.198:0  for rest over http. External groups: PRIV15
*Jan 26 20:27:38.621: %NDBMAN-5-MODEL_RPC_I: R0/0: ndbmand: RPC 'http://cisco.com/ns/yang/Cisco-IOS-XE-logging-ios-actions-rpc:send-log' invoked from 10.42.0.198:0 via RESTCONF user admin session 10744

This behaviour seems to be unnecessarily noisy, and doesn't compare to the cli send log alternative, which is much more surgical in its handling:

cat8kv-01#send log ?
  <0-7>     Severity level of log message
  LINE      Message text
  facility  Set the Facility Name
  <cr>      <cr>

cat8kv-01#send log

Recommending to discontinue this approach - unless there is no better viable alternatives.

[joshhalley]

Did some further testing, so there is another call which may be less noisy, still not perfect, but better than the other approach:

curl -sS -u admin:<password> --insecure -H 'Content-Type: application/yang-data+json' -H 'Accept: application/yang-data+json' -X POST 'https://192.0.2.24/restconf/operations/Cisco-IOS-XE-cli-rpc:config-ios-cli-rpc' -d '{ "Cisco-IOS-XE-cli-rpc:input": { "config-clis": "do send log 6 nginx-on-switch1 cvk0000_ce18f946989346ed93fb8e18d03f514b DEPLOYED " } }'

cat8kv-01#
*Jan 26 20:53:15.530: %SYS-6-USERLOG_INFO: Message from tty65(user id: admin): nginx-on-switch1 cvk0000_ce18f946989346ed93fb8e18d03f514b DEPLOYED
*Jan 26 20:53:15.531: %SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100002 from console as admin on vty4294966927
*Jan 26 20:53:15.500: %DMI-5-AUTH_PASSED: R0/0: dmiauthd: User 'admin' authenticated successfully from 10.42.0.198:0  for rest over http. External groups: PRIV15

[joshhalley]

This needs to be evaluated again when looking more closely into GNMi as a streaming connection method