Add support for session profiles

CONTRIBUTING.rst

@@ -73,7 +73,7 @@ Reporting An Issue/Feature
 Codestyle
 ---------
 This project uses `ruff <https://github.com/astral-sh/ruff>`__ to enforce
-codstyle requirements. We've codified this process using a tool called
+codestyle requirements. We've codified this process using a tool called
 `pre-commit <https://pre-commit.com/>`__. pre-commit allows us to specify a
 config file with all tools required for code linting, and surfaces either a
 git commit hook, or single command, for enforcing these.

botocore/session.py

@@ -101,6 +101,7 @@ def __init__(
         event_hooks=None,
         include_builtin_handlers=True,
         profile=None,
+        session_profiles=None,
     ):
         """
         Create a new Session object.
@@ -125,6 +126,12 @@ def __init__(
             session.  Note that the profile can only be set when
             the session is created.
 
+        :type session_profiles: dict
+        :param session_profiles: A dictionary that is used add or override
+            profile configuration asociated with this session.  The
+            keys are profile names and the values are profile
+            configurations with the same structure as the config file.
+
         """
         if event_hooks is None:
             self._original_handler = HierarchicalEmitter()
@@ -144,6 +151,7 @@ def __init__(
         self._credentials = None
         self._auth_token = None
         self._profile_map = None
+        self._session_profiles = {}
         # This is a dict that stores per session specific config variable
         # overrides via set_config_variable().
         self._session_instance_vars = {}
@@ -157,6 +165,8 @@ def __init__(
         self.session_var_map = SessionVarDict(self, self.SESSION_VARIABLES)
         if session_vars is not None:
             self.session_var_map.update(session_vars)
+        if session_profiles is not None:
+            self._session_profiles = session_profiles
         invoke_initializers(self)
 
     def _register_components(self):
@@ -458,6 +468,7 @@ def full_config(self):
                         self._config['profiles'][profile].update(cred_vars)
             except ConfigNotFound:
                 pass
+            self._config['profiles'].update(self._session_profiles)
         return self._config
 
     def get_default_client_config(self):

tests/unit/test_session.py

@@ -376,6 +376,26 @@ def test_can_get_with_methods(self):
         value = self.session.get_config_variable('region', methods=('env',))
         self.assertEqual(value, 'env-var')
 
+    def test_session_profile_add(self):
+        session = create_session(
+            session_profiles={
+                "test": {
+                    "role_arn": "arn:aws:iam::123456789012:role/test",
+                    "credential_source": "Ec2InstanceMetadata",
+                }
+            }
+        )
+
+        self.assertTrue("test" in session.full_config["profiles"])
+        self.assertEqual(
+            session.full_config["profiles"]["test"]["role_arn"],
+            "arn:aws:iam::123456789012:role/test",
+        )
+        self.assertEqual(
+            session.full_config["profiles"]["test"]["credential_source"],
+            "Ec2InstanceMetadata",
+        )
+
 
 class TestSessionPartitionFiles(BaseSessionTest):
     def test_lists_partitions_on_disk(self):