add string(bool) overload

Author: maorwayn

checker/src/main/java/dev/cel/checker/CelStandardDeclarations.java

@@ -159,6 +159,7 @@ enum StandardFunction {
         Overload.Conversions.INT64_TO_STRING,
         Overload.Conversions.UINT64_TO_STRING,
         Overload.Conversions.DOUBLE_TO_STRING,
+        Overload.Conversions.BOOL_TO_STRING,
         Overload.Conversions.BYTES_TO_STRING,
         Overload.Conversions.TIMESTAMP_TO_STRING,
         Overload.Conversions.DURATION_TO_STRING),
@@ -679,6 +680,9 @@ public enum Conversions implements StandardOverload {
         DOUBLE_TO_STRING(
             CelOverloadDecl.newGlobalOverload(
                 "double_to_string", "type conversion", SimpleType.STRING, SimpleType.DOUBLE)),
+        BOOL_TO_STRING(
+            CelOverloadDecl.newGlobalOverload(
+                "bool_to_string", "type conversion", SimpleType.STRING, SimpleType.BOOL)),
         BYTES_TO_STRING(
             CelOverloadDecl.newGlobalOverload(
                 "bytes_to_string", "type conversion", SimpleType.STRING, SimpleType.BYTES)),

checker/src/test/resources/standardEnvDump.baseline

@@ -256,6 +256,7 @@ declare string {
   function int64_to_string (int) -> string
   function uint64_to_string (uint) -> string
   function double_to_string (double) -> string
+  function bool_to_string (double) -> string
   function bytes_to_string (bytes) -> string
   function timestamp_to_string (google.protobuf.Timestamp) -> string
   function duration_to_string (google.protobuf.Duration) -> string

runtime/src/main/java/dev/cel/runtime/CelStandardFunctions.java

@@ -223,6 +223,7 @@ public enum StandardFunction {
         Conversions.STRING_TO_STRING,
         Conversions.INT64_TO_STRING,
         Conversions.DOUBLE_TO_STRING,
+        Conversions.BOOL_TO_STRING,
         Conversions.BYTES_TO_STRING,
         Conversions.TIMESTAMP_TO_STRING,
         Conversions.DURATION_TO_STRING,
@@ -478,6 +479,7 @@ public enum Conversions implements StandardOverload {
         STRING_TO_STRING(StringOverload.STRING_TO_STRING::newFunctionBinding),
         INT64_TO_STRING(StringOverload.INT64_TO_STRING::newFunctionBinding),
         DOUBLE_TO_STRING(StringOverload.DOUBLE_TO_STRING::newFunctionBinding),
+        BOOL_TO_STRING(StringOverload.BOOL_TO_STRING::newFunctionBinding),
         BYTES_TO_STRING(StringOverload.BYTES_TO_STRING::newFunctionBinding),
         TIMESTAMP_TO_STRING(StringOverload.TIMESTAMP_TO_STRING::newFunctionBinding),
         DURATION_TO_STRING(StringOverload.DURATION_TO_STRING::newFunctionBinding),

runtime/src/main/java/dev/cel/runtime/standard/StringFunction.java

@@ -53,8 +53,11 @@ public enum StringOverload implements CelStandardOverload {
         (celOptions, runtimeEquality) ->
             CelFunctionBinding.from("int64_to_string", Long.class, Object::toString)),
     DOUBLE_TO_STRING(
-        (celOptions, runtimeEquality) ->
-            CelFunctionBinding.from("double_to_string", Double.class, Object::toString)),
+            (celOptions, runtimeEquality) ->
+                    CelFunctionBinding.from("double_to_string", Double.class, Object::toString)),
+    BOOL_TO_STRING(
+            (celOptions, runtimeEquality) ->
+                    CelFunctionBinding.from("bool_to_string", Boolean.class, Object::toString)),
     BYTES_TO_STRING(
         (celOptions, runtimeEquality) ->
             CelFunctionBinding.from(