Support configuration of document storage in agreement settings

Purpose:
Allow the configuration of documentation storage (LOB or S3), with appropriate settings (specifically for S3) for the agreements module, enabling control of the way in which documents are stored.

The requirement is to be able to configure the following information:

Storage to be used: S3 or LOB (latter being database storage)
If S3 is being used additionally:

• S3URL
• S3Key
• S3Secret
• S3Bucket
• S3Prefix

Only users with the appropriate permissions should be able to view and change these options. This will require new permission:
"displayName": "Settings (Agreements): Can view and edit document storage settings",
"description": "Grants permission to view and edit the document storage settings (S3 vs Database) for Agreements."

User story statement(s):

As a systems librarian / system administrator
I want to configure how documents are stored in mod-agreements
so that documents stored with agreements can be stored in an appropriate place (database or S3)

As a systems librarian / system administrator
I want to configure S3 for mod-agreements
so that documents stored with agreements can be stored in S3

Scenarios:

1. Scenario:
   • Given Settings -> Agreements -> General
   • When I view the settings AND I have permission to view and edit document storage settings
   • Then I see an option for "Document storage"
   • 
2. Scenario:
   • Given "Document storage" in the settings
   • When I select "Document storage"
   • Then I see options to choose the document storage to be used "S3" or "Database" (LOB), with "Database" being the default option
   • 
3. Scenario:
   • Given the Document storage settings
   • When I select "Database"
   • Then I see no other options and can click "Save" to save my changes
4. Scenario:
   • Given the Document storage settings
   • When I select "S3"
   • Then I see further options to configure and cannot "Save" until these are completed
5. Scenario:
   • Given the Document storage settings
   • When I select "S3"
   • Then I see options to configure
     • S3URL (must contain a valid URL)
     • S3Key
     • S3Secret
     • S3Bucket
     • S3Prefix
     • 
6. Scenario:
   • Given the Document storage settings
   • When I make changes to the method or S3 options
   • Then the "Save" button becomes active
7. Scenario:
   • Given the Document storage settings
   • When I click the "Save" button
   • Then the the user will be prompted to check they do wish to proceed with the message "Changing the document storage options will affect existing documents in the system, and could make them inaccessible if the configuration is not correct. Consider making a full backup before making any changes. Please confirm you wish to continue and save your changes to the configuration."
   • The user will require the new permission to view and edit document storage settings to be able to successfully save the settings