[WIP] New Link Creation Agent processors

[eddiebrissow]

Missing processor's implementation;

[andre-senna]

See comments in the dev channel

[andre-senna]

There are two things in this new design that I think new to be changed.

(1) Processor are designed to deal with 1 single QueryAnswer. This is bad because we'd need to instantiate one processor for each QueryAnswer and this is a totally unnecessary overhead. And a pointless one, in my opinion, since it doesn't make the design simpler. Processors don't keep any data (or they shouldn't) so the best design here is to instantiate them only once in agent's constructor and use them to process QueryAnswers of multiple requests.

(2) Creation and returning of the created links are split into three methods making the whole process asynchronous. This introduce unnecessary overhead and complexity. I believe the need to tho this is because of the point (1) above. So I think that solving (1) will make it easier to solve (2).

NOTE: to address (1) and (2) we'd need to change the method signature to something like:

    virtual virtual std::vector<std::vector<std::string>> process(QueryAnswer* query_answer);

Which kind of merge the functionality of current constructor, process() and get_links().

[angeloprobst]

                vector<vector<string>> link_tokens;
                auto processor_type = \
                    LinkCreationProcessor::get_processor_type(link_template.front());
                if (processor_type == ProcessorType::PROOF_OF_IMPLICATION) {
                    link_tokens = \
                        implication_processor.process(query_answer, link_template);
                } else if (processor_type == ProcessorType::PROOF_OF_EQUIVALENCE) {
                    link_tokens = \
                        equivalence_processor.process(query_answer, link_template);
                } else {
                    link_tokens = \
                        link_template_processor.process(query_answer, link_template);
                }
                this->create_link(link_tokens, *das_client);

[angeloprobst]

It's an optional but cannot be nullopt?

[angeloprobst]

        if (config == std::nullopt) {
            throw runtime_error("Invalid link template");
        }
        if (config.value().front() == "LIST") {
            LinkCreateTemplateList link_create_template_list(config.value());
            for (auto link_template : link_create_template_list.get_templates()) {
                auto link = \
                    process_template_request(query_answer, link_template);
                links.push_back(link);
            }
        } else {
            LinkCreateTemplate link_template(config.value());
            auto link = \
                process_template_request(query_answer, link_template);
            links.push_back(link);
        }

[angeloprobst]

Please, check the functions params for const-ness and referencing.

Also, if possible, add using namespace std; to the top of the file and remove std:: from the middle of the code to make it cleaner.