Implement Article Model, Schemas, and Decorators

[bryanwong8]

Is your feature request related to a problem? Please describe.
Need to create Article Schemas for serialization and validation. Also need to create decorators to not allow users to access a non-existing Article.

Describe the solution you'd like
Create Decorators and Schemas for Article.

Routes/functions to implement/change

• Create the article_exists decorator
• Create the ArticleFormSchema, ArticleSchema and ArticlesSchema.

Additional context

• Create the Article model in models.py with the following fields:
• title: text (nullable=False)
• cover_image: text (nullable=True)
• content: text (nullable=False)
• date_published: Date (nullable=False)
• likes: int (nullable=False, default=0)
• is_published (nullable=False)
• The article_exists decorator should take the query id from the route and query for the Article. If the Article exists return the args and kwargs. If not return a 404 message saying that "Article does not exist".
• Create the ArticleFormSchema class to contain the following fields:
• title (required)
• cover_image (not required)
• content (not required)
• Create the ArticleSchema that has the following fields:
  • id
• You can create the ArticlesSchema by using the ArticleSchema, but set it to return many models instead.