log matcher: add support for matching against feature flag values

src/bitdrift_public/protobuf/matcher/v1/log_matcher.proto

@@ -95,10 +95,27 @@ message LogMatcher {
       }
     }
 
+    // Base matcher for evaluating the value of a feature flag.
+    message FeatureFlagMatch {
+      string flag_name = 1 [(validate.rules).string = {min_len: 1, max_len: 64}];
+
+      oneof value_match {
+        option (validate.required) = true;
+
+        // Matches against the string value of the feature flag variant. If the variant
+        // is not set we'll match against the empty string.
+        StringValueMatch string_value_match = 2;
+
+        // Matches if the feature flag is set (regardless of variant).
+        IsSetMatch is_set_match = 3;
+      }
+    }
+
     oneof match_type {
       option (validate.required) = true;
       MessageMatch message_match = 1;
       TagMatch tag_match = 2;
+      FeatureFlagMatch feature_flag_match = 3;
     }
   }
 

src/bitdrift_public/protobuf/workflow/v1/workflow.proto

@@ -376,6 +376,8 @@ message Workflow {
 
         // The tag value is the body of the log. If the body is not present, no tag is added.
         bool log_body_extracted = 4;
+
+        FeatureFlagExtracted feature_flag_extracted = 5;
       }
     }
 
@@ -425,4 +427,18 @@ message Workflow {
       Exact exact = 2;
     }
   }
+
+  // A value extracted from the feature flags.
+  message FeatureFlagExtracted {
+    string name = 1 [(validate.rules).string = {min_len: 1}];
+
+    message Exact {
+    };
+
+    // For now we only support exact match, but in the future we might support more complex
+    // extraction logic like regex captures. If not specified, the default is exact match.
+    oneof extraction_type {
+      Exact exact = 2;
+    }
+  }
 }