Task/DES-2623: Add Pydantic models and integration tests for entity metadata

[jarosenb]

Overview:

Initializes the "V2" Projects API and adds Pydantic models for each project metadata schema. An integration test suite confirms that these models exhaustively represent the existing project metadata.

PR Status:

• Ready.
• Work in Progress.
• Hold.

Related Jira tickets:

• DES-2623

Summary of Changes:

• Initial scaffolding for the V2 projects app.
• Add Pydantic models for all existing metadata types.
• Add an integration test suite for verifying the Pydantic models.

Testing Steps:

To run the metadata validations on your machine:

1. from designsafe.apps.projects_v2.tests.schema_integration import validate_entities
2. validate_entities()
   This will validate the schema against all base-level project entities. For other entity types, pass in the name and corresponding Pydantic model.

UI Photos:

Notes: