feat(controlplane) generate mapping for items in CAS

[migmartri]

NOTE: Help for reviewers. Most of this code is generated, what you should take a look at are the changes in internal/data/casmapping.go, internal/biz, and service/attestation

This patch enables a mapping in the DB between the digest of the pieces of evidences (materials) and attestations, as well as the CAS backend and WorkflowRun

• The CASBackendID will be used to solve Being able to download an artifact even if default CAS backend changed #268
• The WorkflowRunID will be used to tackle Enable the public access to materials and attestations in CAS #263

Once the attestation is received in the controlplane, entries in this table for all the materials uploaded in the CAS + the attestation will be stored.

Example

controlplane=# select digest,cas_mapping_workflow_run,cas_mapping_cas_backend from cas_mappings;
                                 digest                                  |       cas_mapping_workflow_run       |       cas_mapping_cas_backend        
-------------------------------------------------------------------------+--------------------------------------+--------------------------------------
 sha256:330ecf0c226ac03baa9094d70e1c2518e20964afe69c2bb30796e21b286d51d7 | a1cccd29-d3b9-4948-9bad-1d00558ca750 | 3f10073c-67cf-4b58-b4c8-3828a05ef1db
 sha256:9f4fd53ef8d7283400d986fd8643b00310a2ae14c164cba795a589143ac31660 | f37ee7ec-9f12-487c-a2f3-06a0b0812183 | 3f10073c-67cf-4b58-b4c8-3828a05ef1db
 sha256:03053df3aa032e40acba3a9dc6ea24f2fc696e52c03cb83e284cd8839b745899 | 415be765-16e1-4802-9a7b-98dc8798dfbd | 3f10073c-67cf-4b58-b4c8-3828a05ef1db
 sha256:ebe2e6ffab93f4b2e2743d3557bd094427ea059adc78cfe2cd330a72f61731e8 | 415be765-16e1-4802-9a7b-98dc8798dfbd | 3f10073c-67cf-4b58-b4c8-3828a05ef1db

The next step in another patch will be to leverage this mapping during download, re: #268

[migmartri]

the linter was complaining here

[danlishka]

Awesome! Looking forward to sharing our attestations in upcoming releases