set default phone provider (#2523)

# What this PR does

Sets a default value for the PHONE_PROVIDER setting and replaces the
value of PHONE_PROVIDER with this default value if it is not valid.

## Which issue(s) this PR fixes

- [#2520](#2520)
- [#2323](#2323)

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

---------

Co-authored-by: Innokentii Konstantinov <innokenty.konstantinov@grafana.com>
Co-authored-by: Joey Orlando <joseph.t.orlando@gmail.com>
Co-authored-by: Joey Orlando <joey.orlando@grafana.com>

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Changed
+
+- Added `PHONE_PROVIDER` configuration check by @sreway ([#2523](https://github.com/grafana/oncall/pull/2523))
+
 ## v1.3.13 (2023-07-17)
 
 ### Changed

engine/apps/phone_notifications/phone_provider.py

@@ -181,4 +181,8 @@ def get_phone_provider() -> PhoneProvider:
     if len(_providers) == 0:
         for provider_alias, importpath in settings.PHONE_PROVIDERS.items():
             _providers[provider_alias] = import_string(importpath)()
+
+    if live_settings.PHONE_PROVIDER not in settings.PHONE_PROVIDERS.keys():
+        return _providers[settings.DEFAULT_PHONE_PROVIDER]
+
     return _providers[live_settings.PHONE_PROVIDER]

engine/settings/base.py

@@ -725,6 +725,7 @@ class BrokerTypes:
 
 # map of phone provider alias to importpath.
 # Used in get_phone_provider function to dynamically load current provider.
+DEFAULT_PHONE_PROVIDER = "twilio"
 PHONE_PROVIDERS = {
     "twilio": "apps.twilioapp.phone_provider.TwilioPhoneProvider",
     # "simple": "apps.phone_notifications.simple_phone_provider.SimplePhoneProvider",
@@ -733,7 +734,7 @@ class BrokerTypes:
 if IS_OPEN_SOURCE:
     PHONE_PROVIDERS["zvonok"] = "apps.zvonok.phone_provider.ZvonokPhoneProvider"
 
-PHONE_PROVIDER = os.environ.get("PHONE_PROVIDER", default="twilio")
+PHONE_PROVIDER = os.environ.get("PHONE_PROVIDER", default=DEFAULT_PHONE_PROVIDER)
 
 ZVONOK_API_KEY = os.getenv("ZVONOK_API_KEY", None)
 ZVONOK_CAMPAIGN_ID = os.getenv("ZVONOK_CAMPAIGN_ID", None)