feat: global annotations support

[migmartri]

Global annotations support.

Similarly to the annotations attached to a material #278, now you can a) define a list of optionally set of annotations at the attestation level. These annotations then will be injected into the resulting attestation and in another patch, exposed to plugins such as the notification ones.

• Annotations that don't have a value, will require the user performing the attestation to inject them during att push command.

So for example, having the following schema with an annotation called asset already pre-populated and another one called version without value.

{
        "schemaVersion":  "v1",
        "annotations":  [
                {
                        "name":  "asset",
                        "value":  "chainloop-oss"
                },
                {
                        "name":  "version"
                }
        ],
        "materials":  [
                {
                        "type":  "SBOM_CYCLONEDX_JSON",
                        "name":  "controlplane-sbom",

During the attestation process, when we init we'll see

$ chainloop att init
INF Attestation initialized! now you can check its status or add materials to it
┌───────────────────┬──────────────────────────────────────┐
│ Initialized At    │ 31 Jul 23 09:16 UTC                  │
├───────────────────┼──────────────────────────────────────┤
│ Workflow          │ 3e4ef02c-0f33-4248-84be-8a55ea2e3cb0 │
│ Name              │ only-sbom                            │
│ Team              │                                      │
│ Project           │ foo                                  │
│ Contract Revision │ 20                                   │
│ Annotations       │ ------                               │
│                   │ asset: chainloop-oss                 │
│                   │ version: [NOT SET]                   │
└───────────────────┴──────────────────────────────────────┘

then the annotation can be provided using the attestation push command

chainloop att push --annotation version=123

Refs #252

[danlishka]

Perfect! Looking forward to seeing annotations in production.