Support updating a new feature in GFE-DB

[pbashyal-nmdp]

We would like to add new features to an existing GFE, eg HLA Amino Acid Position. Create new endpoint to add a feature to a GFE.

Good for creating new novel features.

[lgragert]

It would be very useful if new interfaces were developed to query information about the sequences added to GFE. For example, what is the amino acid residue at a particular position for a particular allele? We built a library that loads amino acid sequence data into a SeqRecord object, similar to GFE. This is the first function we've exposed as a web tool. https://www.transplanttoolbox.org/aa_poly/poly_home/. I would much rather stand this on top of GFE. You could also tie this in with amino acid motifs of particular interest for histocompatibility and immunogenetics, for example putative antibody epitopes. https://www.epregistry.com.br/index/databases/database/ABC/