Add method to send post with multiple attached photos

[ryoryo25]

Description

I've added a function send_images to send a post with multiple attached images.

Changes

• Add function send_images to class Client & AsyncClient
• Rewrite function send_image using send_images (to keep backward compatibility)
• Add an example of usage of send_images

[MarshalX]

Hi! Thank you for contributing! I saw that many people looking for this method. Backward compatibility is awesome. A few notes before deep diving into code:

• we write sync Client and then auto-generate async version. Looks like the generator failed. Probably you wrote the async version by hand. Could you pls fix it?
• speaking of blobls upload in the async version could we try to upload blobs simultaneously? For example, using asyncio.gather. I mean and don't see the reason to wait to upload the previous image to upload a new one
• check on 4 images and no more should be covered already by the model. I guess we could delete this if from here

[ryoryo25]

Thank you for reviewing my code!
I revised the following parts you mentioned.

• Revert the async version of Client
• Delete validation for the number of images
• Modify the code generator of AsyncClient to generate code for uploading blobs simultaneously by using asyncio.gather

  uploads = [self.upload_blob(i) for i in images]

  converts to

  uploads = asyncio.gather(*[self.upload_blob(i) for i in images])

[MarshalX]

thank you! pls check why CI still fails

[ryoryo25]

I've fixed the parts you mentioned. I think CI would be passed.

[MarshalX]

great job!