Proposal to handle breaking changes

[josecelano]

Today in our weekly meeting we were discussing how to handle breaking-change issues.

I will leave here my proposal to discus it. I will start using it if there are no rejections or other proposals to discuss.

1. Label and milestones

• Add a new label Breaking Change and add the label to issues that introduce breaking changes. Make this issues as small as possible.
• Assign the issue with the breaking change to the planned major release where the change will be released.

Good practices

• When possible introduce breaking changes progressively. For example, keeping two methods the old one and the new one for a while. Set the old functionality as deprecated.
• Write good documentation for the breaking change and how to upgrade.
• We should have a proper CHANGELOG.

cc @da2ce7