Debian Group and Project Distribution Keys (schema and model)

What does this MR do?

This is item 7.2 of #5835 (comment 414103286).

Migrations

up:

== 20210505070612 CreatePackagesDebianGroupDistributionKeys: migrating ========
-- create_table(:packages_debian_group_distribution_keys, {})
-- quote_column_name(:public_key)
   -> 0.0001s
-- quote_column_name(:fingerprint)
   -> 0.0001s
   -> 0.0428s
-- quote_table_name("check_f708183491")
   -> 0.0001s
-- quote_table_name("check_bc95dc3fbe")
   -> 0.0001s
-- quote_table_name(:packages_debian_group_distribution_keys)
   -> 0.0000s
-- execute("ALTER TABLE \"packages_debian_group_distribution_keys\"\nADD CONSTRAINT \"check_f708183491\" CHECK (char_length(\"public_key\") <= 524288),\nADD CONSTRAINT \"check_bc95dc3fbe\" CHECK (char_length(\"fingerprint\") <= 255)\n")
   -> 0.0043s
== 20210505070612 CreatePackagesDebianGroupDistributionKeys: migrated (0.0758s) 

== 20210505070812 CreatePackagesDebianProjectDistributionKeys: migrating ======
-- create_table(:packages_debian_project_distribution_keys, {})
-- quote_column_name(:public_key)
   -> 0.0000s
-- quote_column_name(:fingerprint)
   -> 0.0000s
   -> 0.0299s
-- quote_table_name("check_d188f6547f")
   -> 0.0002s
-- quote_table_name("check_9e8a5eef0a")
   -> 0.0001s
-- quote_table_name(:packages_debian_project_distribution_keys)
   -> 0.0000s
-- execute("ALTER TABLE \"packages_debian_project_distribution_keys\"\nADD CONSTRAINT \"check_d188f6547f\" CHECK (char_length(\"public_key\") <= 524288),\nADD CONSTRAINT \"check_9e8a5eef0a\" CHECK (char_length(\"fingerprint\") <= 255)\n")
   -> 0.0027s
== 20210505070812 CreatePackagesDebianProjectDistributionKeys: migrated (0.0459s) 

Down:

== 20210505070612 CreatePackagesDebianGroupDistributionKeys: reverting ========
-- drop_table(:packages_debian_group_distribution_keys)
   -> 0.0088s
== 20210505070612 CreatePackagesDebianGroupDistributionKeys: reverted (0.0319s) 

== 20210505070812 CreatePackagesDebianProjectDistributionKeys: reverting ======
-- drop_table(:packages_debian_project_distribution_keys)
   -> 0.0062s
== 20210505070812 CreatePackagesDebianProjectDistributionKeys: reverted (0.0215s) 

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team