Additional constraints

[alphaville]

Is your feature request related to a problem? Please describe.
We can expand our library of constraints with a few more sets. We can consider sets of the following types:

• Epigraph of the squared Euclidean norm as in this example
• Balls of $\|{}\cdot{}\|_p$, for $p\in[0, \infty)$ (yes, for $p<1$ as well) following this paper
• Affine spaces of the form $\{x: Ax = b\}$, but where $A$ is a linear operator rather than a matrix (in Rust, this will be a closure)

Any additional constraints we could support? Comment below.

Describe the solution you'd like
We should implement these in Rust first, test them, and the take care of the code generation too.