[PB-1551]: Feat/invite users to org

[apsantiso]

This PR is to enable workspace invitations to either new users and already registered users.

Mnemonic should come encrypted from the frontend with the public key of the precreated user or the registered email. Same pattern as we are using for sharing.

Invites should be only accepted if there is enough same left in the workspace. Once an invitation is sent, then that space counts as assigned.

As defined for the MVP, I set the limit to 10 users per workspace.

New Environment variables for sengrid templates:

#Workspaces
WORKSPACES_USER_INVITATION_EMAIL_ID=d-de1ed6df4a9947129c0bf592c808b58d
WORKSPACES_GUEST_USER_INVITATION_EMAIL_ID=d-41b4608fc94a41bca65aab7ed6ccad15

[sg-gs]

To increase the coverage %, try to test at least on the repository the cases where a method should return 0 if the number being expected is null @apsantiso

[sonarqubecloud]

Quality Gate failed

Failed conditions
78.9% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud