Show proper documentation links on all bot user accounts

What does this MR do?

Documentation changes:

• Copies some content from development docs to add a new internal users documentation page.
• Changes internal users link on users' index documentation to link to this new page

Backend changes:

• Adds a new field to API User entity called bot_documentation_url
• New field appears only for user records classified as bot types
• Value of new field is static, linked to help page path covering all bot users
• Removes setting website_url for bots in order to avoid a database maintenance burden due to doc paths changing

Frontend changes:

• Bots will display a link to the added user documentation pages covering all bot users.
• Uses newly added field to display this link.
• If the field is absent in response, no link will be shown.

Closes issue: #330350 (closed)

Screenshots (strongly suggested)

For the popover UI, when the user account lacks a valid website_url attribute:

Before:

After:

Other than this, I ran a GDK instance and created a few bot types (project access token, ghost user, support bot) to test that their new default bot_documentation_url links show up in popovers and go to a valid, local help page.

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.