feat: add bulk method

[cgroschupp]

Because the bulk endpoint can handle create, update and delete operations, it is not necessary to have a separate method for each operation, so I implement it differently than in #9

Docs: https://desec.readthedocs.io/en/latest/dns/rrsets.html#bulk-operations

[ldez]

Hello,

I can see several problems with this approach:

• the returned RRSets are not managed
• the delete requires knowing the API (This is achieved by sending a bulk request with a RRset that has an empty records list [])

I updated PR #9, I'm still thinking about the best approach.

[ldez]

@cgroschupp can you check something for me?

Inside PR #9, the status code of a bulk creation is 201, I'm not sure about that, can you check it?

[cgroschupp]

Only the Post request returns a status code of 201. I have changed the code.

[cgroschupp]

Hello,

I can see several problems with this approach:

* the returned RRSets are not managed

* the delete requires knowing the API (This is achieved by sending a bulk request with a RRset that has an empty records list `[]`)

I updated PR #9, I'm still thinking about the best approach.

I think the first point is covered by my additional commit.
On the second point, I don't really have a good idea for changing this. One way is to add a deleted bool to the rrset and set it in bulk to [].

[ldez]

I merged PR #9, with some modifications.

I see you added touched field, can you create another PR dedicated to that?

[ldez]

I close this PR in favor of #9