feat(receiver-mock): add querying the spans and traces by span name

src/rust/receiver-mock/README.md

@@ -47,7 +47,7 @@ The following endpoints provide information about received traces:
   It accepts a list of key value pairs being an attribute set that the span will
   have to fullfil in order to be returned.
   Attribute values can be omitted in which case only presence of a particular attribute
-  will be checked.
+  will be checked. `__name__` is handled specially as it will be matched against the span name.
 
   Exemplary output:
 
@@ -102,7 +102,7 @@ The following endpoints provide information about received traces:
   It accepts a list of key value pairs being an attribute set.
   If any span in a trace contains all of these attributes, this trace will be in the list.
   Attribute values can be omitted in which case only presence of a particular attribute
-  will be checked.
+  will be checked. Similarly as in `/spans-list`, `__name__` is handled specially as it will be matched against the name of any span.
 
   Exemplary output:
 

src/rust/receiver-mock/src/traces/mod.rs

@@ -46,8 +46,18 @@ impl std::fmt::Display for Span {
 }
 
 fn is_span_ok(span: &Span, params: &HashMap<String, String>) -> bool {
-    // TODO: This can be expanded to query by other parameters. As for now, it only filters by label.
     for (key, value) in params.iter() {
+        // Identically as in the metric's case,
+        // we use "__name__" as key for span's name
+        // to keep the querying simple.
+        if key == "__name__" {
+            if span.name == *value {
+                continue;
+            } else {
+                return false;
+            }
+        }
+
         if let Some(val) = span.attributes.get(key) {
             if val.eq(value) {
                 continue;