poc/create-alter-for-metrics:

### Commit Message

 Enhance error handling in `batch_builder.rs` and `error.rs`

 - **`batch_builder.rs`**:
   - Replaced `todo!` with specific error handling for invalid timestamp and field value types using `InvalidTimestampValueTypeSnafu` and `InvalidFieldValueTypeSnafu`.

 - **`error.rs`**:
   - Added new error variants `InvalidTimestampValueType` and `InvalidFieldValueType` with descriptive messages.
   - Updated `status_code` method to handle new error types with `StatusCode::Unexpected`.

Signed-off-by: Lei, HUANG <mrsatangel@gmail.com>

src/servers/src/batch_builder.rs

@@ -296,14 +296,16 @@ impl BatchEncoder {
 
             // process timestamp and field. We already know the position of timestamps and values in [TableBuilder].
             let ValueData::TimestampMillisecondValue(ts) =
+                // safety: timestamp values cannot be null
                 row.value_at(0).value_data.as_ref().unwrap()
             else {
-                todo!("return an error")
+                return error::InvalidTimestampValueTypeSnafu.fail();
             };
             self.timestamps.push(*ts);
 
+            // safety: field values cannot be null in prom remote write
             let ValueData::F64Value(val) = row.value_at(1).value_data.as_ref().unwrap() else {
-                todo!("return an error")
+                return error::InvalidFieldValueTypeSnafu.fail();
             };
             self.value.push(*val);
         }

src/servers/src/error.rs

@@ -645,6 +645,20 @@ pub enum Error {
         #[snafu(implicit)]
         location: Location,
     },
+
+    #[snafu(display(
+        "Invalid timestamp value type in row data, expected TimestampMillisecondValue"
+    ))]
+    InvalidTimestampValueType {
+        #[snafu(implicit)]
+        location: Location,
+    },
+
+    #[snafu(display("Invalid field value type in row data, expected F64Value"))]
+    InvalidFieldValueType {
+        #[snafu(implicit)]
+        location: Location,
+    },
 }
 
 pub type Result<T, E = Error> = std::result::Result<T, E>;
@@ -771,6 +785,9 @@ impl ErrorExt for Error {
             CommonMeta { source, .. } => source.status_code(),
             Operator { source, .. } => source.status_code(),
             EncodePrimaryKey { source, .. } => source.status_code(),
+            InvalidTimestampValueType { .. } | InvalidFieldValueType { .. } => {
+                StatusCode::Unexpected
+            }
         }
     }