Crypto scheme to map data to users in a way that is anonymous to database server
I'm not sure this threat model is realistic, since I would expect an adversary to want to shutdown the entire site, instead of just censoring specific &quot;contributors&quot; :-).
To protect from this (and from the users becoming de-anonymized) one would likely use an anonymity network such as Tor.

The website should not be able to see that data content in clear text. - this problem is fixable by implementing database encryption with key derived from user password and kept in session, and dumped at the end.

The problem with this, is that the data will be unencrypted at the server's location for some time - worse, the server has the key.
Lets assume, that the server is compromised, and malicious:
Then it could easily obtain a copy of every new document, and of old documents by storing the password, when the respective user logs in again.
A solution to this problem would be to have contributors encrypt data using the public key of the recipient.
However, if you use asymmetric cryptography on the client side, someone has to perform the encryption.
You don't want the website to do this for several reasons:

JavaScript (which would likely be required) is a large attack surface - if the server is compromised, and users of the website are required to enable JS, they are exposed to more risk.

If the server is compromised, it could swap the encryption for nothing, without the users noticing.


Therefore, you would likely need an external program, such as gpg or age.
Unfortunately, by now, we have achieved usability levels close to that of encrypted email :-(.

What I need is a hint in order to implement multiple cryptographic functions in a system that will allow a website to map data to an account anonymously.

As I already said, I don't think this is a realistic requirement.
Additionally, I'm not aware of any protocols that solve this problem.
However, ring-signatures could maybe be used to authenticate users. Using ring-signatures, a user could prove that they are part of a larger user-group. Then, the server can't determine which specific user they are, but could allow them to submit documents for upload.
I'm not sure on the specifics, and there are many ways the protocol design of this could go wrong. A first step would be, to determine the exact requirements.