feat(gcs): allow setting a token directly (#4978)

* feat: add token to gcsconfig

* feat: add bearer token to header requests

* feat: add token to builder

* feat: make token optional

* feat: place token within header

* feat: pass scope to gcs core

* feat: return token directly from load_token if set

* refactor: use tuple match for token/scope handling

* fix: use default scope set for gcscore

* fix: scope must be valid

* revert: do not change sign logic

* revert: do not change sign_query logic

core/src/services/gcs/backend.rs

@@ -74,6 +74,10 @@ pub struct GcsConfig {
     pub disable_vm_metadata: bool,
     /// Disable loading configuration from the environment.
     pub disable_config_load: bool,
+    /// A Google Cloud OAuth2 token.
+    ///
+    /// Takes precedence over `credential` and `credential_path`.
+    pub token: Option<String>,
 }
 
 impl Debug for GcsConfig {
@@ -214,6 +218,12 @@ impl GcsBuilder {
         self
     }
 
+    /// Provide the OAuth2 token to use.
+    pub fn token(mut self, token: String) -> Self {
+        self.config.token = Some(token);
+        self
+    }
+
     /// Disable attempting to load credentials from the GCE metadata server.
     pub fn disable_vm_metadata(mut self) -> Self {
         self.config.disable_vm_metadata = true;
@@ -354,6 +364,8 @@ impl Builder for GcsBuilder {
                 client,
                 signer,
                 token_loader,
+                token: self.config.token,
+                scope: scope.to_string(),
                 credential_loader: cred_loader,
                 predefined_acl: self.config.predefined_acl.clone(),
                 default_storage_class: self.config.default_storage_class.clone(),

core/src/services/gcs/core.rs

@@ -53,6 +53,8 @@ pub struct GcsCore {
     pub client: HttpClient,
     pub signer: GoogleSigner,
     pub token_loader: GoogleTokenLoader,
+    pub token: Option<String>,
+    pub scope: String,
     pub credential_loader: GoogleCredentialLoader,
 
     pub predefined_acl: Option<String>,
@@ -76,6 +78,10 @@ static BACKOFF: Lazy<ExponentialBuilder> =
 
 impl GcsCore {
     async fn load_token(&self) -> Result<Option<GoogleToken>> {
+        if let Some(token) = &self.token {
+            return Ok(Some(GoogleToken::new(token, usize::MAX, &self.scope)));
+        }
+
         let cred = { || self.token_loader.load() }
             .retry(&*BACKOFF)
             .await