Indicate that max_token_ttl is required for OIDC auth methods

[am-ak]

• Include an example for OIDC auth method
• correct the description of max_token_ttl that it is a required argument for OIDC auth method

[im2nguyen]

Suggested change

	Deine an `OIDC` auth method:
	```hcl
	resource "consul_acl_auth_method" "oidc" {
	name = "auth0"
	type = "oidc"
	max_token_ttl = "5m"
	config_json = jsonencode({
	"OIDCDiscoveryURL": "https://<AUTH0_DOMAIN>/",
	"OIDCClientID": "<AUTH0_CLIENT_ID>",
	"OIDCClientSecret": "<AUTH0_CLIENT_SECRET>",
	"BoundAudiences": ["<AUTH0_CLIENT_ID>"],
	"AllowedRedirectURIs": [
	"http://localhost:8550/oidc/callback",
	"http://localhost:8500/ui/oidc/callback"
	],
	"ClaimMappings": {
	"http://consul.internal/first_name": "first_name",
	"http://consul.internal/last_name": "last_name"
	},
	"ListClaimMappings": {
	"http://consul.internal/groups": "groups"
	}
	})
	}
	```
	Define an `OIDC` auth method:
	```hcl
	resource "consul_acl_auth_method" "oidc" {
	name = "auth0"
	type = "oidc"
	max_token_ttl = "5m"
	config_json = jsonencode({
	"OIDCDiscoveryURL": "https://<AUTH0_DOMAIN>/",
	"OIDCClientID": "<AUTH0_CLIENT_ID>",
	"OIDCClientSecret": "<AUTH0_CLIENT_SECRET>",
	"BoundAudiences": ["<AUTH0_CLIENT_ID>"],
	"AllowedRedirectURIs": [
	"http://localhost:8550/oidc/callback",
	"http://localhost:8500/ui/oidc/callback"
	],
	"ClaimMappings": {
	"http://consul.internal/first_name": "first_name",
	"http://consul.internal/last_name": "last_name"
	},
	"ListClaimMappings": {
	"http://consul.internal/groups": "groups"
	}
	})
	}
	```

[remilapeyre]

Hi @am-ak, thank you very much for reporting this issue. I had missed this when working on consul_acl_auth_mode, it is pretty rare that arguments can be optional or required based on another one.

I kept most of your implementation but migrated the consul_acl_auth_method documentation to the tfplugindocs framework as this is an ongoing migration that I do as we update the documentation of each resources. This is what most of my commits are about, sorry for the noise.

I also updated the example in the documentation to use the one in the Consul documentation.

Thanks for your contribution!