feat: google cloud platform pubsub plugin integration

[Ikari]

This PR have two changes:

• Google's pubsub integration: hathor_pubsub.js is a plugin that allows the wallet to send external notifications to a pubsub topic
• Fixing multisig param types: when deploying on some cloud environments (such as GCP Cloud Run), the multisig_seed${x}max_signatures and multisig_seed${x}num_signatures are threated as strings, not integers. When starting the multisig, the comparison made with this params is a exact on ( "===") so it fails. By parsing the params before we can avoid that.

src/controllers/index.controller.js Ln 100-101:

  const mconfig = config.multisig[multisigKey];
    console.log('mconfig', mconfig);
    if (!(mconfig
           && (mconfig.total && mconfig.numSignatures && mconfig.pubkeys)
           && (mconfig.pubkeys.length === mconfig.total)
           && (mconfig.numSignatures <= mconfig.total))) {
      // Missing multisig items
      console.error(`Improperly configured multisig for seed ${multisigKey}.`);
      res.send({
        success: false,
        message: `Improperly configured multisig for seed ${multisigKey}.`
      });
      return;

[pedroferreira1]

@Ikari the PR is approved, it just needs a rebase so we can continue with the merge

[Ikari]

@Ikari the PR is approved, it just needs a rebase so we can continue with the merge

Rebased!

[pedroferreira1]

@Ikari we've fixed a bug in codecov, so we can make the CI succeed. Can you do one more rebase please, to update your branch, so we can check if the CI completes?

[Ikari]

@pedroferreira1 sure thing, branch updated.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 89.04%. Comparing base (fb2faae) to head (00b780c).

Files	Patch %	Lines
src/plugins/hathor_pubsub.js	0.00%	9 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #450      +/-   ##
==========================================
- Coverage   89.53%   89.04%   -0.50%     
==========================================
  Files          51       52       +1     
  Lines        2151     2163      +12     
  Branches      406      409       +3     
==========================================
  Hits         1926     1926              
- Misses        208      217       +9     
- Partials       17       20       +3     

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