Standardize all models

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Despite the title, this is more of a refactoring. A lot of the models contain similar fields, and there was a lot of repeated code. In an effort to adhere to DRY (Don't Repeat Yourself), the best course of action was to go ahead and add in a BaseTemplateDoc.cs, which contains fields for doc Id, doc Title, and doc Date. All these might possibly be null (which is something to further look into).

In an effort to be more conservative, this change won't be merged yet, as it might break some things. The following should be done:

• [x] Check that changes done won't break the bot due to differences in the database
  • NOTE: docs in the database should be altered vs the code, as annoying as that may be
• [x] Double-check all references that make use of the different docs
  • NOTE: this shouldn't break things currently, but one never knows

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Explored the concepts behind null safety. In a nutshell, ! and ? postfix operators change the nullability state of a variable. If ! is used, the reference is non-nullable, which means it can not be null. In a similar sense, the use of ? denotes the reference is nullable, which means it can be null.

As it stands, some files (perhaps namely the BaseTemplateDoc.cs) make use of null!, which tells the compiler that null is not a nullable value, which can be dangerous. It's best to perhaps indicate and enforce that some fields in the doc may be nullable.

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Went ahead and checked all Model references. All appear in the DatabaseService.cs file, and as mentioned here and here, the file should also be refactored, but should be tracked in a separate issue.

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Local JSON files have been updated and uploaded to the local database. Will do a quick test before going ahead and merging all the commits to main.

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In hindsight, it might be difficult to try and test these changes in a dev environment. I think it may now be necessary to introduce a unit testing framework. According to Microsoft documentation, they do provide one for .NET code. Should look into it. An issue should also be opened to track this.

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58 has been created to document the need for a testing framework. Issue will also depend on this pull request as well. No way to try and avoid two completely different things from being done in the same PR due to the necessity to test the above changes.

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There's been quite a bit of major changes being done, all due to having changed a single class implementation.

Good news: now we should be able to develop unit tests now!

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So I think everything has been done accordingly... maybe... hopefully.

Fingers crossed!