AzureStorage does not allow creation of signed URLs for upload

[CorentinGoodays]

Summary
The AzureStorage class in the django-storages module does not currently support generating signed URLs for uploads due to the hardcoded BlobSasPermissions(read=True) in the url() method. This limitation restricts users from creating SAS tokens with upload permissions.

Environment
django-storages version: All

Steps to Reproduce
Attempt to generate a signed URL for upload using the AzureStorage class.
Observe that the generated URL only has read permissions.

Expected Behavior
Users should be able to generate signed URLs with different permissions, including upload permissions.

Actual Behavior
The url() method only generates URLs with read permissions, as BlobSasPermissions(read=True) is hardcoded.

Proposed Solution
Allow the url() method to accept a mode parameter to specify different permissions. Here is a possible implementation:

diff --git a/storages/backends/azure_storage.py b/storages/backends/azure_storage.py
index 69b0213..435bc9a 100644
--- a/storages/backends/azure_storage.py
+++ b/storages/backends/azure_storage.py
@@ -309,9 +309,10 @@ class AzureStorage(BaseStorage):
     # azure expects time in UTC
     return datetime.utcnow() + timedelta(seconds=expire)

-    def url(self, name, expire=None, parameters=None):
+    def url(self, name, expire=None, parameters=None, mode="r"):
     name = self._get_valid_path(name)
     params = parameters or {}
+    permission = BlobSasPermissions.from_string(mode)

     if expire is None:
         expire = self.expiration_secs
@@ -326,7 +327,7 @@ class AzureStorage(BaseStorage):
         name,
         account_key=self.account_key,
         user_delegation_key=user_delegation_key,
-        permission=BlobSasPermissions(read=True),
+        permission=permission,
         expiry=expiry,
         **params,
     )

Testing
I have tested this solution in my environment and confirmed that it allows generating signed URLs with different permissions, including upload permissions. Using these generated URLs, I successfully uploaded a file to Azure Storage.