feat(IamAssumeAuthenticator): introduce new authenticator type

This commit introduces the new IamAssumeAuthenticator which
will fetch an IAM access token using the IAM getToken operation's
"assume" grant type.  The resulting access token allows the
application to assume the identity of a trusted profile,
similar to the "sudo" feature of Linux.

Signed-off-by: Phil Adams <[email protected]>

Author: padamstx

.secrets.baseline

@@ -3,7 +3,7 @@
     "files": "package-lock.json|^.secrets.baseline$",
     "lines": null
   },
-  "generated_at": "2024-09-03T23:09:01Z",
+  "generated_at": "2024-10-01T20:10:03Z",
   "plugins_used": [
     {
       "name": "AWSKeyDetector"
@@ -70,23 +70,55 @@
         "hashed_secret": "91dfd9ddb4198affc5c194cd8ce6d338fde470e2",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 72,
+        "line_number": 73,
+        "type": "Secret Keyword",
+        "verified_result": null
+      },
+      {
+        "hashed_secret": "4f51cde3ac0a5504afa4bc06859b098366592c19",
+        "is_secret": false,
+        "is_verified": false,
+        "line_number": 222,
+        "type": "Secret Keyword",
+        "verified_result": null
+      },
+      {
+        "hashed_secret": "e87559ed7decb62d0733ae251ae58d42a55291d8",
+        "is_secret": false,
+        "is_verified": false,
+        "line_number": 224,
+        "type": "Secret Keyword",
+        "verified_result": null
+      },
+      {
+        "hashed_secret": "12f4a68ed3d0863e56497c9cdb1e2e4e91d5cb68",
+        "is_secret": false,
+        "is_verified": false,
+        "line_number": 288,
+        "type": "Secret Keyword",
+        "verified_result": null
+      },
+      {
+        "hashed_secret": "c837b75d7cd93ef9c2243ca28d6e5156259fd253",
+        "is_secret": false,
+        "is_verified": false,
+        "line_number": 292,
         "type": "Secret Keyword",
         "verified_result": null
       },
       {
         "hashed_secret": "98635b2eaa2379f28cd6d72a38299f286b81b459",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 407,
+        "line_number": 526,
         "type": "Secret Keyword",
         "verified_result": null
       },
       {
         "hashed_secret": "47fcf185ee7e15fe05cae31fbe9e4ebe4a06a40d",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 510,
+        "line_number": 629,
         "type": "Secret Keyword",
         "verified_result": null
       }
@@ -104,23 +136,23 @@
         "hashed_secret": "d4c3d66fd0c38547a3c7a4c6bdc29c36911bc030",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 46,
+        "line_number": 47,
         "type": "Secret Keyword",
         "verified_result": null
       },
       {
         "hashed_secret": "8318df9ecda039deac9868adf1944a29a95c7114",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 49,
+        "line_number": 50,
         "type": "Secret Keyword",
         "verified_result": null
       },
       {
         "hashed_secret": "9a66213cc16d178fdbf9f4da6b7bd92497fda404",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 55,
+        "line_number": 56,
         "type": "Secret Keyword",
         "verified_result": null
       }
@@ -183,6 +215,16 @@
         "verified_result": null
       }
     ],
+    "src/test/java/com/ibm/cloud/sdk/core/test/security/IamAssumeAuthenticatorTest.java": [
+      {
+        "hashed_secret": "333f0f8814d63e7268f80e1e65e7549137d2350c",
+        "is_secret": false,
+        "is_verified": false,
+        "line_number": 57,
+        "type": "Secret Keyword",
+        "verified_result": null
+      }
+    ],
     "src/test/java/com/ibm/cloud/sdk/core/test/security/JsonWebTokenTest.java": [
       {
         "hashed_secret": "c6ba9cef42f298486a61546fefd03a4177e60a99",
@@ -294,7 +336,7 @@
         "hashed_secret": "f2e7745f43b0ef0e2c2faf61d6c6a28be2965750",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 115,
+        "line_number": 127,
         "type": "Secret Keyword",
         "verified_result": null
       }