Add fields to each items default section

[priscilasolis]

Resolves: #17

Description: There is currently no ability to add custom fields outside of a section with the 1Password Terraform provider.

Solution: A list of fields can now be defined outside of a section. Applying this is similar to how we currently implement fields inside a section.

It's important to note that in order to make this happen some other updates had to take place:

• A secure_note category is added because there was no way to add fields without a password (also referenced in #66).
• Include note_value in the resource as it was previously set in the data source.
• Delete purpose value from from the fields as it can cause a collision with the note_value argument when NOTES is set as the purpose.
• Fix bug where it wasn't capturing deleted fields from an existing item and therefore wasn't trying to recreate the deleted fields when running terraform apply.

[edif2008]

Hey @priscilasolis! 👋🏻

Thank you for making this contribution and apologies for the late response.

I wanted to bring to your attention that we've recently migrated to the new terraform-plugin-framework. With this big change, this PR is no longer applicable to the latest version of the provider.

We really appreciate the time and effort that you have already put into this PR. If you have some additional time to spare and you're still interested in having this change applied, please go ahead and modify this PR to make it compatible with the latest v2 version of this provider, at which point we'd be happy to review it again.

I've also noticed that your commits are not signed. This repository requires all commits to be signed. If you work on changing this PR to make it compatible with the latest v2 version of the provider, it would be great to have your commits signed as well.

Here is some guidelines in achieving this.

Sign commits with 1Password

You can also sign commits using 1Password, which lets you sign commits with biometrics without the signing key leaving the local 1Password process. Learn how to [use 1Password to sign your commits](https://developer.1password.com/docs/ssh/git-commit-signing/).

Sign commits with ssh-agent

Follow the steps below to set up commit signing with `ssh-agent`: 1. [Generate an SSH key and add it to `ssh-agent`](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent) 2. [Add the SSH key to your GitHub account](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/adding-a-new-ssh-key-to-your-github-account) 3. [Configure `git` to use your SSH key for commit signing](https://docs.github.com/en/authentication/managing-commit-signature-verification/telling-git-about-your-signing-key#telling-git-about-your-ssh-key)

Sign commits with gpg

Follow the steps below to set up commit signing with `gpg`: 1. [Generate a GPG key](https://docs.github.com/en/authentication/managing-commit-signature-verification/generating-a-new-gpg-key) 2. [Add the GPG key to your GitHub account](https://docs.github.com/en/authentication/managing-commit-signature-verification/adding-a-gpg-key-to-your-github-account) 3. [Configure `git` to use your GPG key for commit signing](https://docs.github.com/en/authentication/managing-commit-signature-verification/telling-git-about-your-signing-key#telling-git-about-your-gpg-key)