breaking-change: Manage authorities

[valentindeaconu]

This PR introduces authorities' management flows (including the UI).

An authority represents a namespace. Under that particular namespace, all resources are served to Terraform using the authority keys, name, and policy.

From the web interface, an authenticated user will be able to:

• Create a new authority;
• Remove an existing authority with all its data (gpg keys, api keys, providers and modules);
• Allocate an API key for an existing authority;
• Remove an existing API key from an existing authority.

From the API, an authenticated user (using an API key) will be able to:

• Upload a new provider under the API key's authority namespace;
• Upload a new module under the API key's authority namespace.

Note: The API key should be generated for that particular namespace.

However, this PR also introduces several breaking changes:

• Adds a new owner column to the authority table;
• Removes owner_email and owner_name from authority_api_keys table;
• Adds authority_id column to the providers table;
• Removes namespace column from providers table;
• Adds authority_id column to the modules table;
• Removes namespace column from modules table;
• Rename authority table to authorities;
• API endpoints for POST and DELETE methods for both providers and modules no longer take the namespace as an input parameter.

It's recommended to fully reconstruct the database.