Feat: Additional Salesforce auth methods (#641)

* Salesforce different auth methods

* Small test, readme adjusted

* Typo fixes, correct imports, and get_proxies improved

Author: anuunchin

sources/salesforce/README.md

@@ -37,21 +37,76 @@ Here, we chose BigQuery as the destination. Alternatively, you can also choose r
 
 ## Setup verified source and pipeline example
 
-To grab credentials and initialize the verified source, please refer to the [full documentation here.](https://dlthub.com/docs/dlt-ecosystem/verified-sources/salesforce)
+To initialize the verified source, please refer to the [full documentation here.](https://dlthub.com/docs/dlt-ecosystem/verified-sources/salesforce)
 
-## Add credentials
+## Add credentials and configs
 
 1. Open `.dlt/secrets.toml`.
-2. Enter the user name, password and security token:
+2. Enter the username, password and security token:
     ```toml
     # put your secret values and credentials here. do not share this file and do not push it to github
-    [sources.salesforce]
+    [sources.salesforce.credentials]
     user_name = "please set me up!" # Salesforce user name
     password = "please set me up!" # Salesforce password
     security_token = "please set me up!" # Salesforce security token generated
     ```
+
+   Alternatively, you may authenticate using any method supported by the underlying `simple_salesforce` library. For instructions on obtaining these credentials, please consult Salesforce’s documentation.
+
+    - IP-whitelist + organization ID:
+        ```toml
+        [sources.salesforce.credentials]
+        user_name = "please set me up!" 
+        password = "please set me up!" 
+        organization_id = "please set me up!"
+        ```    
+
+    - Session ID + instance:
+        ```toml
+        [sources.salesforce.credentials]
+        session_id = "please set me up!" 
+        instance = "please set me up!" # OR
+        instance_url = "please set me up!"
+        ```    
+
+    - JWT method:
+        ```toml
+        [sources.salesforce.credentials]
+        user_name = "please set me up!" 
+        consumer_key = "please set me up!" 
+        privatekey_file = "please set me up!" # OR
+        privatekey = "please set me up!"
+        instance_url = "please set me up!" # Optional
+        ```    
+
+    - Connected app method:
+        ```toml
+        [sources.salesforce.credentials]
+        user_name = "please set me up!" 
+        password = "please set me up!" 
+        consumer_key = "please set me up!"
+        consumer_secret = "please set me up!"
+        ```    
 
-3. Enter credentials for your chosen destination as per the [docs.](https://dlthub.com/docs/dlt-ecosystem/destinations/)
+    - Client credentials method:
+        ```toml
+        [sources.salesforce.credentials]
+        consumer_key = "please set me up!"
+        consumer_secret = "please set me up!"
+        domain = "please set me up!"
+        ```    
+
+3. You can set up the following optional configs in your `.dlt/config.toml` file that will be used to connect to Salesforce:
+
+    ```toml
+    [sources.salesforce]
+    domain = "please set me up!" # Set to "test" if sandbox
+    version = "please set me up!" # Version of the Salesforce API to use, defaults to 59.0 
+    proxies = "please set me up!" # Mapping of protocols to proxy servers
+    client_id = "please set me up!" # App identifier for Salesforce API usage tracking
+    ```
+
+4. Enter credentials for your chosen destination as per the [docs.](https://dlthub.com/docs/dlt-ecosystem/destinations/)
 
 ## Run the pipeline example
 

sources/salesforce/__init__.py

@@ -10,35 +10,22 @@
 from dlt.sources import DltResource
 from dlt.sources import incremental
 
-from typing import Iterable
+from typing import Iterable, Optional
 
 import dlt
-from simple_salesforce import Salesforce
+from dlt.sources.helpers.requests import Session
 from dlt.common.typing import TDataItem
 
-
-from .helpers import get_records
+from .helpers.records import get_records
+from .helpers.client import SalesforceAuth, make_salesforce_client
 
 
 @dlt.source(name="salesforce")
 def salesforce_source(
-    user_name: str = dlt.secrets.value,
-    password: str = dlt.secrets.value,
-    security_token: str = dlt.secrets.value,
+    credentials: SalesforceAuth = dlt.secrets.value,
+    session: Optional[Session] = None,
 ) -> Iterable[DltResource]:
-    """
-    Retrieves data from Salesforce using the Salesforce API.
-
-    Args:
-        user_name (str): The username for authentication. Defaults to the value in the `dlt.secrets` object.
-        password (str): The password for authentication. Defaults to the value in the `dlt.secrets` object.
-        security_token (str): The security token for authentication. Defaults to the value in the `dlt.secrets` object.
-
-    Yields:
-        DltResource: Data resources from Salesforce.
-    """
-
-    client = Salesforce(user_name, password, security_token)
+    client = make_salesforce_client(credentials, session)
 
     # define resources
     @dlt.resource(write_disposition="replace")