REFACTOR: encapsulate DB ops in own methods

[HilkopterBob]

We should encapsulate external Databases in an Interface (interface DB) with embedded Methods like:

• sign in
• connect
• other CRUD's

this seperates the user (eg. handler) from the product specific implementations.

With that we can select which db-product (eg. surreal, postgres, cassandra) we use to instantiate the db.
This can be selected by an optional config flag (shouldn't be included in preset).

This enables us to slowly migrate from one db to another (if needed) without:

• touching a hundred different functions
• having to wait on a migration branch to finish before adding new stuff that depends on db

example(s):

db/db.go:

type Database interface {
    SignIn() error
    Connect() error
    Close() error
    QueryUser(id int) (*User, error)

db/surreal.go, db/postgres.go and db/cassandra.go now only have to implement all methods of Database to for example satisfy a handler that requests a Database from FX:

func GetAllAgentsHandler(db *db.Database){
// logic here
}

[HilkopterBob]

If this gets implemented successfully and proves a viable option at this state we can do the same for viper (config management), the tracer (currently OpenTelemetry, but we could use the go built in one for smaller runtime impact during development)