feat(server): add fallback to GITHUB_TOKEN if installation token fails (#1887)

- Attempts to retrieve a GitHub App Installation token first
- Falls back to GITHUB_TOKEN if the installation token fails
- Logs a warning on failure of installation token retrieval

Author: LeoColman

shared-internal/src/main/kotlin/io/github/typesafegithub/workflows/shared/internal/GithubUtils.kt

@@ -1,7 +1,10 @@
 package io.github.typesafegithub.workflows.shared.internal
 
+import io.github.oshai.kotlinlogging.KotlinLogging.logger
 import kotlinx.coroutines.runBlocking
 
+private val logger = logger { }
+
 /**
  * Returns a token that should be used to make authorized calls to GitHub,
  * or null if no token was configured.
@@ -10,13 +13,10 @@ import kotlinx.coroutines.runBlocking
  */
 fun getGithubAuthTokenOrNull(): String? =
     runBlocking {
-        (System.getenv("GITHUB_TOKEN") ?: getInstallationAccessToken())
-            .also {
-                if (it == null) {
-                    println(ERROR_NO_CONFIGURATION)
-                }
-            }
-    }
+        runCatching { getInstallationAccessToken() }
+            .onFailure { logger.warn(it) { "Failed to get GitHub App Installation token, falling back to GITHUB_TOKEN." } }
+            .getOrNull() ?: System.getenv("GITHUB_TOKEN")
+    }.also { if (it == null) logger.warn { ERROR_NO_CONFIGURATION } }
 
 /**
  * Returns a token that should be used to make authorized calls to GitHub,