Implement Tag Model, Schemas, and Decorators

[bryanwong8]

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

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

Routes/functions to implement/change

• Create the tag_exists decorator
• Create the TagFormSchema, TagSchema and TagsSchema.

Additional context

• Create the Tag model in models.py with the following fields:
• name: text (nullable=False)
• summary: text (nullable=False)
• submission_guideline: text (nullable=False)
• about: text (nullable=False)
• emoji: text (nullable=False)
• users: many to many relationship. Allow Users and Tags to connected to each other
• The tag_exists decorator should take the query id from the route and query for the Tag. If the Tag exists return the args and kwargs. If not return a 404 message saying that "Tag does not exist".
• Create the TagFormSchema class to contain the following fields:
• name (required)
• summary (required)
• submission_guidelines (required)
• about (required)
• Create the TagSchema that has the following fields:
  • id
• You can create the TagsSchema by using the TagSchema, but set it to return many models instead.