Add GET method for Issuer /credentials and /offers endpoints

[nanderstabel]

Description

This will ensure that all Credentials and Offers can be queried.

A ListAllQuery need to be added to agent_store similar to the way it is implemented in fn holder_state in both postgres.rs and in_memory.rs.
The endpoints handlers need to be added to agent_api_rest

The following can be copied into fn issuer_state (including the lines that initialize the all_credentials and all_offers View Repositories):

    // Create custom-queries for the offer aggregate.
    let all_credentials_query = ListAllQuery::new(all_credentials.clone(), "all_credentials");
    let all_offers_query = ListAllQuery::new(all_offers.clone(), "all_offers");

Important detail is that in order for the view_id's not to overlap with each other those current three lines in fn holder_state need to be changed to:

    // Create custom-queries for the offer aggregate.
    let all_holder_credentials_query = ListAllQuery::new(all_credentials.clone(), "all_holder_credentials");
    let all_received_offers_query = ListAllQuery::new(all_offers.clone(), "all_received_offers");

This means that all other code occurrences of all_credentials and all_offers need to be updated as well (including inside the init.sql file):
all_credentials --> all_holder_credentials
all_offers --> all_received_offers

The View Repositories are added to agent_holder::state::ViewRepositories in fn holder_state. The exact same thing needs to be implemented in fn issuer_state. This means that agent_issuer::state::ViewRepositories needs to be updated to include the all_credentials and all_offers View Repositories the same way it is done in agent_holder::state::ViewRepositories:

type Queries = ViewRepositories<
    dyn ViewRepository<CredentialView, Credential>,
    dyn ViewRepository<AllCredentialsView, Credential>, // <-- this
    dyn ViewRepository<OfferView, Offer>,
    dyn ViewRepository<AllOffersView, Offer>, // <-- this
>;

pub struct ViewRepositories<C1, C2, O1, O2>
where
    C1: ViewRepository<CredentialView, Credential> + ?Sized,
    C2: ViewRepository<AllCredentialsView, Credential> + ?Sized, // <-- this
    O1: ViewRepository<OfferView, Offer> + ?Sized,
    O2: ViewRepository<AllOffersView, Offer> + ?Sized, // <-- this
{
    pub credential: Arc<C1>,
    pub all_credentials: Arc<C2>, // <-- this
    pub offer: Arc<O1>,
    pub all_offers: Arc<O2>, // <-- this
}

impl Clone for Queries {
    fn clone(&self) -> Self {
        ViewRepositories {
            credential: self.credential.clone(),
            all_credentials: self.all_credentials.clone(), // <-- this
            offer: self.offer.clone(),
            all_offers: self.all_offers.clone(), // <-- this
        }
    }
}

This also means that AllCredentialsView and AllOffersView can be copy-pasted from the agent_holder crate. In the same fashion as earlier mentioned, the following occurrences should be renamed:

• AllCredentialsView --> AllHolderCredentialsView
• AllOffersView --> AllReceivedOffersView

Motivation

Improves UniCore's utility

Resources

n/a

To-do List

• Add AllCredentialsView and AllOffersView
• Add GET method for /credentials
• Add GET method for /offers