re-enable stderr logs in tests (#2215)

## Does this PR need a docs update or release note?

- [x] ⛔ No 

## Type of change

- [x] 🐛 Bugfix
- [x] 🤖 Test
- [x] 💻 CI/Deployment

## Test Plan

- [x] 💪 Manual

.github/workflows/ci.yml

@@ -208,6 +208,7 @@ jobs:
           CORSO_M365_TEST_USER_ID: ${{ secrets.CORSO_M365_TEST_USER_ID }}
           CORSO_SECONDARY_M365_TEST_USER_ID: ${{ secrets.CORSO_SECONDARY_M365_TEST_USER_ID }}
           CORSO_PASSPHRASE: ${{ secrets.INTEGRATION_TEST_CORSO_PASSPHRASE }}
+          CORSO_LOG_FILE: stderr
           LOG_GRAPH_REQUESTS: true
         run: |
           set -euo pipefail
@@ -219,7 +220,7 @@ jobs:
           -p 1          \
           ./... 2>&1 | tee ./testlog/gotest.log | gotestfmt -hide successful-tests
 
-      # Upload the original go test log as an artifact for later review.
+      # Upload the original go test output as an artifact for later review.
       - name: Upload test log
         if: failure()
         uses: actions/upload-artifact@v3

.github/workflows/load_test.yml

@@ -53,6 +53,7 @@ jobs:
           AZURE_CLIENT_SECRET: ${{ secrets.AZURE_CLIENT_SECRET }}
           AZURE_TENANT_ID: ${{ secrets.AZURE_TENANT_ID }}
           CORSO_LOAD_TESTS: true 
+          CORSO_LOG_FILE: stderr
           CORSO_M365_LOAD_TEST_USER_ID: ${{ secrets.CORSO_M365_LOAD_TEST_USER_ID }}
           CORSO_M365_LOAD_TEST_ORG_USERS: ${{ secrets.CORSO_M365_LOAD_TEST_ORG_USERS }}
           CORSO_PASSPHRASE: ${{ secrets.CORSO_PASSPHRASE }}

src/pkg/logger/logger.go

@@ -106,6 +106,11 @@ func PreloadLoggingFlags() (string, string) {
 		return "info", dlf
 	}
 
+	// if not specified, attempt to fall back to env declaration.
+	if len(logfile) == 0 {
+		logfile = os.Getenv("CORSO_LOG_FILE")
+	}
+
 	if logfile == "-" {
 		logfile = "stdout"
 	}