Added fix for bug #8278 to read tag values from YAML files (#8354)

# Description

This PR adds a fix for reading tag values from YAML file.

A tag in YAML file is denoted by using the exclamation point ("!")
symbol.

For example - Key: !Value

Additional passing test has also been added supporting the bug fix - 
- `test_convert_yaml_value_to_nu_value_for_tagged_values`

The fix passes all the below required tests suites locally - 

>To check standard code formatting.
- `cargo fmt --all -- --check` (`cargo fmt --all` applies these changes)
>To check that you're using the standard code style.
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect`
>To check that all tests pass
- `cargo test --workspace`

---------

Co-authored-by: Nitin Londhe <nitin.londhe@genmills.com>

crates/nu-command/src/formats/from/yaml.rs

@@ -174,6 +174,30 @@ fn convert_yaml_value_to_nu_value(
 
             Value::from(collected)
         }
+        serde_yaml::Value::Tagged(t) => {
+            let tag = &t.tag;
+            let value = match &t.value {
+                serde_yaml::Value::String(s) => {
+                    let val = format!("{} {}", tag, s).trim().to_string();
+                    Value::String { val, span }
+                }
+                serde_yaml::Value::Number(n) => {
+                    let val = format!("{} {}", tag, n).trim().to_string();
+                    Value::String { val, span }
+                }
+                serde_yaml::Value::Bool(b) => {
+                    let val = format!("{} {}", tag, b).trim().to_string();
+                    Value::String { val, span }
+                }
+                serde_yaml::Value::Null => {
+                    let val = format!("{}", tag).trim().to_string();
+                    Value::String { val, span }
+                }
+                v => convert_yaml_value_to_nu_value(v, span, val_span)?,
+            };
+
+            value
+        }
         serde_yaml::Value::Null => Value::nothing(span),
         x => unimplemented!("Unsupported YAML case: {:?}", x),
     })
@@ -314,4 +338,63 @@ mod test {
 
         test_examples(FromYaml {})
     }
+
+    #[test]
+    fn test_convert_yaml_value_to_nu_value_for_tagged_values() {
+        struct TestCase {
+            input: &'static str,
+            expected: Result<Value, ShellError>,
+        }
+
+        let test_cases: Vec<TestCase> = vec![
+            TestCase {
+                input: "Key: !Value ${TEST}-Test-role",
+                expected: Ok(Value::Record {
+                    cols: vec!["Key".to_string()],
+                    vals: vec![Value::test_string("!Value ${TEST}-Test-role")],
+                    span: Span::test_data(),
+                }),
+            },
+            TestCase {
+                input: "Key: !Value test-${TEST}",
+                expected: Ok(Value::Record {
+                    cols: vec!["Key".to_string()],
+                    vals: vec![Value::test_string("!Value test-${TEST}")],
+                    span: Span::test_data(),
+                }),
+            },
+            TestCase {
+                input: "Key: !Value",
+                expected: Ok(Value::Record {
+                    cols: vec!["Key".to_string()],
+                    vals: vec![Value::test_string("!Value")],
+                    span: Span::test_data(),
+                }),
+            },
+            TestCase {
+                input: "Key: !True",
+                expected: Ok(Value::Record {
+                    cols: vec!["Key".to_string()],
+                    vals: vec![Value::test_string("!True")],
+                    span: Span::test_data(),
+                }),
+            },
+            TestCase {
+                input: "Key: !123",
+                expected: Ok(Value::Record {
+                    cols: vec!["Key".to_string()],
+                    vals: vec![Value::test_string("!123")],
+                    span: Span::test_data(),
+                }),
+            },
+        ];
+
+        for test_case in test_cases {
+            let doc = serde_yaml::Deserializer::from_str(test_case.input);
+            let v: serde_yaml::Value = serde_yaml::Value::deserialize(doc.last().unwrap()).unwrap();
+            let result = convert_yaml_value_to_nu_value(&v, Span::test_data(), Span::test_data());
+            assert!(result.is_ok());
+            assert!(result.ok().unwrap() == test_case.expected.ok().unwrap());
+        }
+    }
 }