Implement file parser for NSD's (and soon Unbound)'s TSIG config-snippet-in-a-file for use in Cascade

[maertsen]

NSD:

key:
        name: test.key
        algorithm: hmac-sha256
        secret: "B22jiD30pKL541XsOZ28y+NxbcIRoGqnumH2SFC8QDE="

It appears the NSD config file format also allows the secret string to be unquoted.

Unbound (in a dev branch):

tsig-key:
       name: test.key
       algorithm: hmac-sha256
       secret: "B22jiD30pKL541XsOZ28y+NxbcIRoGqnumH2SFC8QDE="

An alias will be added in a future release of NSD, so it supports tsig-key: going forward. This creates a yaml-like format Cascade will implement as well. This issue is for Domain to implement the required parsing with Cascade as a user in https://github.com/NLnetLabs/cascade/blob/70bc25ecf38cc5af25684914360c30415637a1cd/crates/cli/src/commands/tsig.rs#L108.

[maertsen]

For reference (but not in-scope for this issue), these are some of the other file formats around:

BIND9's tsig-keygen:

$ tsig-keygen example.com
key "example.com" {
	algorithm hmac-sha256;
	secret "+oBiPrlOk83X+PkNz6QEpzHhulQRct1YRuyqt3XeapM=";
};

ldns-keygen overloads the file format for DNSSEC keys, encoding the name as part of the filename:

Private-key-format: v1.2
Algorithm: 159 (HMAC_SHA256)
Key: B22jiD30pKL541XsOZ28y+NxbcIRoGqnumH2SFC8QDE=

test.key.	IN	KEY	0 3 159 B22jiD30pKL541XsOZ28y+NxbcIRoGqnumH2SFC8QDE=

[pusateri]

It’s great to see this feature being added. I built my own but will be glad to remove my own code when I get a chance to test this. Thank-you.