Implementation for text data type

[kgodey]

Problem

Users will want to store text data in columns. We should allow them to do so and implement this type appropriately in the backend.

Proposed solution

We should support Text types in Mathesar and allow users to use them.

Tasks that need to completed:

• Design for text data type #234
• Handle VARCHAR data type in the backend. #404
• Handle TEXT data type in the backend. #405
• Handle CHAR data type in the backend. #407
• Implement filtering options for Text types. #406
• Implement grouping for Text types. #408
• Frontend implementation for Text Mathesar type #254

Additional context

Related issues and PRs:

• Mapping DB data types to Mathesar data types #269
• Controlled casting #127
• Infer column type two #135

[mathemancer]

Unless we have a specific reason to use TEXT, we should probably use VARCHAR for the column type even when unlimited. This will make it easier to work with. (There shouldn't really be any difference in the DB between TEXT and unlimited-length VARCHAR w.r.t. performance and whatnot.)

[kgodey]

@mathemancer Updated the ticket. I also added a section about reflecting existing TEXT fields correctly.

[rootxnet]

Working on it.

[kgodey]

Closing this since all subtasks are done.