Commit-Confirm Mechanic for PND

Description

This MR introduces a commit-confirm mechanic for changes to ONDs. A change created in a pending-state. A commit of this change by the operator pushed the change to the given OND. If the commit is not confirmed within 10 minutes (default. Use the GOSDN_CHANGE_TIMEOUT environment variable to change the timeout) is is rolled back automatically.

Related Issue

Closes #99 (closed)

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

nucleus/principalNetworkDomain.go

@@ -51,7 +51,7 @@ func NewPND(name, description string, id uuid.UUID, sbi SouthboundInterface) (Pr
 		errChans:         make(map[uuid.UUID]chan error),
 	}
 	if err := pnd.sbic.add(sbi); err != nil {
-		return nil, &ErrAlreadyExists{item: sbi}
+		return nil, err
 	}
 	return pnd, nil
 }