feat(snap): use updated environment variable injection

[MonicaisHer]

For details on the new scheme for setting environment variables, please refer to edgexfoundry/edgex-go#3986.
Signed-off-by: Mengyi Wang [email protected]

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PR Checklist

Please check if your PR fulfills the following requirements:

• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• I am not introducing a new dependency (add notes below if you are)
• I have added unit tests for the new feature or bug fix (if not, why?) N/A - they are in the imported module Add tests for snap config options canonical/edgex-snap-testing#53
• I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• I have opened a PR for the related docs change (if not, why?)

Testing Instructions

1. Set up:

snap install edgexfoundry --edge
snap install edgex-app-service-configurable --channel="edge/pr-407"
snap set edgex-app-service-configurable profile=rules-engine

2. Enable config and set a global config value:

$ snap set edgex-app-service-configurable config-enabled=true
$ snap set edgex-app-service-configurable config.service-startupmsg="testing injection"

$ snap start edgex-app-service-configurable
Started.

$ snap logs -n=all edgex-app-service-configurable | grep "testing injection"
app=app-rules-engine source=service.go:203 msg="testing injection"

3. Set a app-specific value:

$ snap set edgex-app-service-configurable apps.app-service-configurable.config.service-port=11111

$ snap restart edgex-app-service-configurable
Restarted.

$ snap logs -n=all edgex-app-service-configurable | grep "11111"
msg="Starting HTTP Web Server on address localhost:11111"

New Dependency Instructions (If applicable)

[farshidtz]

Thanks. LGTM.

Validate the error handling:

$ snap set edgex-app-service-configurable config.service-startupmsg="testing injection"
error: cannot perform the following tasks:
- Run configure hook of "edgex-app-service-configurable" snap (run hook "configure": 
-----
edgex-app-service-configurable.configure: could not process options: 'config.' and 'apps.' options are allowed only when config-enabled is true.

WARNING: Setting config-enabled=true will unset existing 'env.' options and ignore future sets!!
-----)

$ snap set edgex-app-service-configurable config-enabled=true
$ snap set edgex-app-service-configurable apps.app-service-configurable.config.service.port=11111
error: cannot perform the following tasks:
- Run configure hook of "edgex-app-service-configurable" snap (run hook "configure": edgex-app-service-configurable.configure: could not process options: error converting config key to environment variable key: config key must not contain dots: service.port)

Test:

$ snap set edgex-app-service-configurable config-enabled=true
$ snap set edgex-app-service-configurable config.service-startupmsg="testing injection"
$ snap start edgex-app-service-configurable 
Started.
$ snap logs -n=all edgex-app-service-configurable | grep "testing injection"
2022-04-26T11:19:13+02:00 edgex-app-service-configurable.app-service-configurable[50155]: level=INFO ts=2022-04-26T09:19:13.04886399Z app=app-rules-engine source=variables.go:352 msg="Variables override of 'Service.StartupMsg' by environment variable: SERVICE_STARTUPMSG=testing injection"
2022-04-26T11:19:13+02:00 edgex-app-service-configurable.app-service-configurable[50155]: level=INFO ts=2022-04-26T09:19:13.073178783Z app=app-rules-engine source=variables.go:352 msg="Variables override of 'Service.StartupMsg' by environment variable: SERVICE_STARTUPMSG=testing injection"
2022-04-26T11:19:13+02:00 edgex-app-service-configurable.app-service-configurable[50155]: level=INFO ts=2022-04-26T09:19:13.104004057Z app=app-rules-engine source=service.go:203 msg="testing injection"

$ snap set edgex-app-service-configurable apps.app-service-configurable.config.service-port=11111
$ snap restart edgex-app-service-configurable
Restarted.
$ snap logs -n=all edgex-app-service-configurable | grep "11111"
2022-04-26T11:19:49+02:00 edgex-app-service-configurable.app-service-configurable[50464]: level=INFO ts=2022-04-26T09:19:49.654567422Z app=app-rules-engine source=variables.go:352 msg="Variables override of 'Service.Port' by environment variable: SERVICE_PORT=11111"
2022-04-26T11:19:49+02:00 edgex-app-service-configurable.app-service-configurable[50464]: level=INFO ts=2022-04-26T09:19:49.669203327Z app=app-rules-engine source=variables.go:352 msg="Variables override of 'Service.Port' by environment variable: SERVICE_PORT=11111"
2022-04-26T11:19:49+02:00 edgex-app-service-configurable.app-service-configurable[50464]: level=INFO ts=2022-04-26T09:19:49.696564382Z app=app-rules-engine source=server.go:162 msg="Starting HTTP Web Server on address localhost:11111"

$ cat /var/snap/edgex-app-service-configurable/current/config/res/app-service-configurable.env 
export SERVICE_STARTUPMSG="testing injection"
export SERVICE_PORT="11111"