Adding JWT verifier.

Still missing:
- Caching of the already checked JWTs (although it could be done at an
  upper layer).
- Caching of the jwks_uri to avoid 2 roundtrips for each verification.
diff --git a/tools/run_tests/sources_and_headers.json b/tools/run_tests/sources_and_headers.json
index eb2514f..91f6317 100644
--- a/tools/run_tests/sources_and_headers.json
+++ b/tools/run_tests/sources_and_headers.json
@@ -524,6 +524,20 @@
     ], 
     "headers": [], 
     "language": "c", 
+    "name": "grpc_jwt_verifier_test", 
+    "src": [
+      "test/core/security/jwt_verifier_test.c"
+    ]
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "gpr_test_util", 
+      "grpc", 
+      "grpc_test_util"
+    ], 
+    "headers": [], 
+    "language": "c", 
     "name": "grpc_print_google_default_creds_token", 
     "src": [
       "test/core/security/print_google_default_creds_token.c"
@@ -566,6 +580,20 @@
     ], 
     "headers": [], 
     "language": "c", 
+    "name": "grpc_verify_jwt", 
+    "src": [
+      "test/core/security/verify_jwt.c"
+    ]
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "gpr_test_util", 
+      "grpc", 
+      "grpc_test_util"
+    ], 
+    "headers": [], 
+    "language": "c", 
     "name": "hpack_parser_test", 
     "src": [
       "test/core/transport/chttp2/hpack_parser_test.c"
@@ -8691,6 +8719,7 @@
       "src/core/security/base64.h", 
       "src/core/security/credentials.h", 
       "src/core/security/json_token.h", 
+      "src/core/security/jwt_verifier.h", 
       "src/core/security/secure_endpoint.h", 
       "src/core/security/secure_transport_setup.h", 
       "src/core/security/security_connector.h", 
@@ -8872,6 +8901,8 @@
       "src/core/security/google_default_credentials.c", 
       "src/core/security/json_token.c", 
       "src/core/security/json_token.h", 
+      "src/core/security/jwt_verifier.c", 
+      "src/core/security/jwt_verifier.h", 
       "src/core/security/secure_endpoint.c", 
       "src/core/security/secure_endpoint.h", 
       "src/core/security/secure_transport_setup.c",