chore: Update MSRV to 1.91.0 (apache#2204)

## Which issue does this PR close?
apache#2199 requires a bump to MSRV
1.91.0. This version is within the policy of this project.
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- Closes #.

## What changes are included in this PR?

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Author: xanderbailey

Cargo.toml

@@ -36,7 +36,7 @@ version = "0.8.0"
 license = "Apache-2.0"
 repository = "https://github.com/apache/iceberg-rust"
 # Check the MSRV policy in README.md before changing this
-rust-version = "1.88"
+rust-version = "1.91"
 
 [workspace.dependencies]
 anyhow = "1.0.72"

bindings/python/Cargo.toml

@@ -19,7 +19,7 @@
 edition = "2024"
 homepage = "https://rust.iceberg.apache.org"
 name = "pyiceberg_core_rust"
-rust-version = "1.88"
+rust-version = "1.91"
 version = "0.8.0"
 # This crate is used to build python bindings, we don't want to publish it
 publish = false

crates/iceberg/src/spec/snapshot.rs

@@ -38,11 +38,12 @@ pub const UNASSIGNED_SNAPSHOT_ID: i64 = -1;
 
 /// Reference to [`Snapshot`].
 pub type SnapshotRef = Arc<Snapshot>;
-#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, Clone)]
+#[derive(Debug, Default, Serialize, Deserialize, PartialEq, Eq, Clone)]
 #[serde(rename_all = "lowercase")]
 /// The operation field is used by some operations, like snapshot expiration, to skip processing certain snapshots.
 pub enum Operation {
     /// Only data files were added and no files were removed.
+    #[default]
     Append,
     /// Data and delete files were added and removed without changing table data;
     /// i.e., compaction, changing the data file format, or relocating data files.
@@ -75,12 +76,6 @@ pub struct Summary {
     pub additional_properties: HashMap<String, String>,
 }
 
-impl Default for Operation {
-    fn default() -> Operation {
-        Self::Append
-    }
-}
-
 #[derive(Debug, PartialEq, Eq, Clone)]
 /// Row range of a snapshot, contains first_row_id and added_rows_count.
 pub struct SnapshotRowRange {

crates/integrations/datafusion/src/physical_plan/scan.rs

@@ -126,7 +126,7 @@ impl ExecutionPlan for IcebergTableScan {
         self
     }
 
-    fn children(&self) -> Vec<&Arc<(dyn ExecutionPlan + 'static)>> {
+    fn children(&self) -> Vec<&Arc<dyn ExecutionPlan + 'static>> {
         vec![]
     }
 

rust-toolchain.toml

@@ -20,5 +20,5 @@
 #
 # The channel is exactly same day for our MSRV.
 [toolchain]
-channel = "nightly-2025-06-23"
+channel = "nightly-2025-10-27"
 components = ["rustfmt", "clippy"]