feat: Add UI for configuring SAML in Flagsmith

[novakzaballa]

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Changes

• Add UI for configuring SAML in Flagsmith wrapped with the saml_configuration flag.

How did you test this code?

• Use an organisation with an enterprise plan
• Go to Organisation Settings -> SAML tab
• Create a SAML configuration

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[github-actions]

Uffizzi Preview deployment-52416 was deleted.

[matthewelwell]

@novakzaballa I've fixed a couple of minor issues here, but there are some fundamental issues that need resolving. We will, for example, need to add a new endpoint in the SAML repository (which I will work on now).

[matthewelwell]

I've added a new list endpoint in the PR here which we will need to update this code to use. It's also worth noting that we allow multiple SamlConfiguration objects per organisation, so this PR will need to be updated to handle that case - it seems like it only supports a single configuration at the moment.

Some other changes that will need to be made:

1. We should validate the name attribute as it needs to be a valid URL path parameter. This means we should restrict the input to only alphanumeric + - and _.
2. We need to make sure that we handle errors from the API since the name field is unique across all organisations in the platform.
3. We should add a tooltip explaining what the name field is: "An alphanumeric string to uniquely identify the SAML configuration. You will use this as the 'Organisation name' when logging in via the Flagsmith login page. Must only include alphanumeric characters or hyphens / underscores."
4. The SamlConfiguration endpoints use the name field as the lookup field whereas this PR seems to be trying to use the numeric id field after creation.
5. The IdP metadata can only be XML, and will be multiline. Can we update the input accordingly? Can the syntax validation be locked to XML perhaps?

We should also note that (in the near future), we will want to also be able to manage a list of attribute mappings (which consist of a string input, and a select box (values TBC). So we should consider that when designing the UI to allow for multiple SamlConfiguration objects.

[matthewelwell]

I've tested the UI aspects and all seems good now.

Added a few comments for some typos / improvements to the documentation.

[matthewelwell]

Approved with one more minor typo (which I'll fix now)