Revise DATABRICKS_API_TOKEN as DATABRICKS_TOKEN (#5796)

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In the [Databricks
integration](https://python.langchain.com/en/latest/integrations/databricks.html)
and [Databricks
LLM](https://python.langchain.com/en/latest/modules/models/llms/integrations/databricks.html),
we suggestted users to set the ENV variable `DATABRICKS_API_TOKEN`.
However, this is inconsistent with the other Databricks library. To make
it consistent, this PR changes the variable from `DATABRICKS_API_TOKEN`
to `DATABRICKS_TOKEN`

After changes, there is no more `DATABRICKS_API_TOKEN` in the doc
```
$ git grep DATABRICKS_API_TOKEN|wc -l
0

$ git grep DATABRICKS_TOKEN|wc -l
8
```
cc @hwchase17 @dev2049 @mengxr since you have reviewed the previous PRs.

docs/integrations/databricks.ipynb

@@ -58,7 +58,7 @@
     "### Optional Parameters\n",
     "There following parameters are optional. When executing the method in a Databricks notebook, you don't need to provide them in most of the cases.\n",
     "* `host`: The Databricks workspace hostname, excluding 'https://' part. Defaults to 'DATABRICKS_HOST' environment variable or current workspace if in a Databricks notebook.\n",
-    "* `api_token`: The Databricks personal access token for accessing the Databricks SQL warehouse or the cluster. Defaults to 'DATABRICKS_API_TOKEN' environment variable or a temporary one is generated if in a Databricks notebook.\n",
+    "* `api_token`: The Databricks personal access token for accessing the Databricks SQL warehouse or the cluster. Defaults to 'DATABRICKS_TOKEN' environment variable or a temporary one is generated if in a Databricks notebook.\n",
     "* `warehouse_id`: The warehouse ID in the Databricks SQL.\n",
     "* `cluster_id`: The cluster ID in the Databricks Runtime. If running in a Databricks notebook and both 'warehouse_id' and 'cluster_id' are None, it uses the ID of the cluster the notebook is attached to.\n",
     "* `engine_args`: The arguments to be used when connecting Databricks.\n",

docs/modules/models/llms/integrations/databricks.ipynb

@@ -163,14 +163,14 @@
    ],
    "source": [
     "# Otherwise, you can manually specify the Databricks workspace hostname and personal access token \n",
-    "# or set `DATABRICKS_HOST` and `DATABRICKS_API_TOKEN` environment variables, respectively.\n",
+    "# or set `DATABRICKS_HOST` and `DATABRICKS_TOKEN` environment variables, respectively.\n",
     "# See https://docs.databricks.com/dev-tools/auth.html#databricks-personal-access-tokens\n",
     "# We strongly recommend not exposing the API token explicitly inside a notebook.\n",
     "# You can use Databricks secret manager to store your API token securely.\n",
     "# See https://docs.databricks.com/dev-tools/databricks-utils.html#secrets-utility-dbutilssecrets\n",
     "\n",
     "import os\n",
-    "os.environ[\"DATABRICKS_API_TOKEN\"] = dbutils.secrets.get(\"myworkspace\", \"api_token\")\n",
+    "os.environ[\"DATABRICKS_TOKEN\"] = dbutils.secrets.get(\"myworkspace\", \"api_token\")\n",
     "\n",
     "llm = Databricks(host=\"myworkspace.cloud.databricks.com\", endpoint_name=\"dolly\")\n",
     "\n",

langchain/llms/databricks.py

@@ -114,7 +114,7 @@ def get_default_api_token() -> str:
     """Gets the default Databricks personal access token.
     Raises an error if the token cannot be automatically determined.
     """
-    if api_token := os.getenv("DATABRICKS_API_TOKEN"):
+    if api_token := os.getenv("DATABRICKS_TOKEN"):
         return api_token
     try:
         api_token = get_repl_context().apiToken
@@ -123,7 +123,7 @@ def get_default_api_token() -> str:
     except Exception as e:
         raise ValueError(
             "api_token was not set and cannot be automatically inferred. Set "
-            f"environment variable 'DATABRICKS_API_TOKEN'. Received error: {e}"
+            f"environment variable 'DATABRICKS_TOKEN'. Received error: {e}"
         )
     # TODO: support Databricks CLI profile
     return api_token
@@ -186,7 +186,7 @@ class Databricks(LLM):
     """Databricks personal access token.
     If not provided, the default value is determined by
 
-    * the ``DATABRICKS_API_TOKEN`` environment variable if present, or
+    * the ``DATABRICKS_TOKEN`` environment variable if present, or
     * an automatically generated temporary token if running inside a Databricks
       notebook attached to an interactive cluster in "single user" or
       "no isolation shared" mode.

langchain/sql_database.py

@@ -150,7 +150,7 @@ class SQLDatabase:
                 hostname. Defaults to None.
             api_token (Optional[str]): The Databricks personal access token for
                 accessing the Databricks SQL warehouse or the cluster. If not provided,
-                it attempts to fetch from 'DATABRICKS_API_TOKEN'. If still unavailable
+                it attempts to fetch from 'DATABRICKS_TOKEN'. If still unavailable
                 and running in a Databricks notebook, a temporary token for the current
                 user is generated. Defaults to None.
             warehouse_id (Optional[str]): The warehouse ID in the Databricks SQL. If
@@ -197,7 +197,7 @@ class SQLDatabase:
         default_api_token = context.apiToken if context else None
         if api_token is None:
             api_token = utils.get_from_env(
-                "api_token", "DATABRICKS_API_TOKEN", default_api_token
+                "api_token", "DATABRICKS_TOKEN", default_api_token
             )
 
         if warehouse_id is None and cluster_id is None: