Add Azure Blob Storage tasks

[frsann]

Thanks for contributing to Prefect!

Please describe your work and make sure your PR:

• adds new tests (if appropriate)
• updates CHANGELOG.md (if appropriate)
• updates docstrings for any new functions or function arguments, including docs/outline.toml for API reference docs (if appropriate)

Note that your PR will not be reviewed unless all three boxes are checked.

What does this PR change?

Adds Azure Blob Storage tasks.

Why is this PR important?

Azure Blob Storage users can upload and download stuff.

[marvin-robot]

Here I am, brain the size of a planet and they ask me to welcome you to Prefect.

So, welcome to the community @frsann! 🎉 🎉

[codecov]

Codecov Report

Merging #1538 into master will increase coverage by 0.03%.
The diff coverage is 100%.

[joshmeek]

This looks really great! Would you also mind adding this Task and yourself to CHANGELOG.md?

[frsann]

@joshmeek Sorry about that, totally forgot about it. Updated it in ee16fae.

[joshmeek]

Awesome! This is a great addition! Thanks @frsann

[dazzag24]

Hi,
Looks like a great addition.

One key improvement would be to allow users to use a SAS token rather than the ACCOUNT_KEY
e.g.

from azure.storage.blob import BlockBlobService

bs = BlockBlobService(account_name=<account_name>, sas_token=<sas_token>)

Using SAS tokens is considered more secure than having to share you ACCOUNT_NAME and ACCOUNT_KEY with potentially untrusted services. See more details here:

https://docs.microsoft.com/en-us/azure/storage/common/storage-sas-overview

See also the emulator that may be useful for testing without the cost implications of using real credentials.
https://docs.microsoft.com/en-us/azure/storage/common/storage-use-azurite

Thanks

[joshmeek]

@dazzag24 Great suggestion! Feel free to open a feature request!