Blobs upload proposal

[nikooo777]

1. send sdblob in this format:

type request struct {
	hash string
	sdblob []byte
}

2. server checks the blocklist to see if it wants the stream
3. server checks if the sdblob is already in our system
   3.1) if the sd blob exists, respond with a list of blobs it needs
   3.2) if the sd blob doesn't exist, store the sd blob, save the blobs in the DB with is_stored=0, respond with a list of the blobs it needs (all of them)
4. client sends one blob at a time with the following format

type request struct {
	hash string
	blob []byte
	size int	
}

5. server checks that the uploaded blob has the correct hash and size, saves the blob to S3, sets is_stored=1 in the database, responds with a success
6. optionally we should add an endpoint that accepts a list of sdblob hashes and returns whether the sdblob is needed or not and if the sdblob is already stored, a list of blobs that are missing
   the server thus has to implement the following endpoints:
   /sdblob POST
   accepts:

type request struct {
	hash string
	sdblob []byte
}

returns:

type response struct{
	success bool
	error *error
	type data struct {
		required_blobs []string
	}
}

/blob POST
accepts:

type request struct {
	hash string
	blob []byte
	size int	
}

returns:

type response struct{
	success bool
	error *error
}

/sdblobs POST
accepts:

type request struct {
	hashes []string
}

returns:

type response struct{
	success bool
	error *error
	type data struct {
		required_sdblobs []string
		required_blobs []struct{
			sdhash string
			missing_blobs []string
		}
	}
}