feat: implement comparison skeleton

This commit lays out the general idea of how the ComparisonData struct will work. It is expandable and I'm sure we will add more to it as time goes on.

src/common/comparison/text.rs

@@ -0,0 +1,36 @@
+use super::Comparison;
+use crate::common::ValueType;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize, Debug)]
+pub enum TextComparison {
+    Matches,
+    NotMatches,
+    Contains,
+    NotContains,
+}
+
+impl Comparison for TextComparison {
+    fn evaluate(&self, comp_value: &ValueType, target_value: &ValueType) -> Result<bool, String> {
+        // All text comparisons require that the comp.member points to a Some(string) in the student_info,
+        // and that the target_value is also a Some(string).
+        let student_value = match comp_value {
+            ValueType::String(Some(value)) => value,
+            _ => return Err("Student value is not a string".into()),
+        };
+
+        let target_value = match target_value {
+            ValueType::String(Some(value)) => value,
+            _ => return Err("Target value is not a string".into()),
+        };
+
+        let matched = match self {
+            TextComparison::Matches => student_value == target_value,
+            TextComparison::NotMatches => student_value != target_value,
+            TextComparison::Contains => student_value.contains(target_value),
+            TextComparison::NotContains => !student_value.contains(target_value),
+        };
+
+        Ok(matched)
+    }
+}