Update Composition Functions content to v1beta1

This updates all current documentation of Composition Functions in the
master directory to reflect the new v1beta1 implementation.

Signed-off-by: Nic Cope <[email protected]>

content/master/concepts/compositions.md

@@ -41,8 +41,8 @@ Optionally, Compositions also support:
 * [Modifying and patching](#changing-resource-fields) resource settings.
 * [Storing connection details](#storing-connection-details) and secrets
   generated by the managed resources.
-* Using [Composition functions](#composition-functions) to allow custom 
-  programs to run alongside the Composition. 
+* Using [Composition Functions](#composition-functions) to template resources
+  using custom programs. 
 * Creating a 
   [custom check of when a resource is ready](#resource-readiness-checks) 
   to use. 
@@ -664,40 +664,59 @@ spec:
 The [EnvironmentConfigs]({{<ref "./environment-configs" >}}) page has 
 more information on EnvironmentConfigs options and usage.
 
-### Composition functions
+### Use Composition functions
 
-Composition functions (`XFNs`) are containers executing any code you define.
-Composition functions can read and write to any resource in the Composition
-they're attached to. This allows composition functions to perform complex
-operations to patch fields, determine if a resource is ready for use or notify
-an external system about the details of resource. 
+Composition functions (or just Functions, for short) are custom programs that
+template Crossplane resources. You can write a Function to template resources
+using a general purpose programming language like Go or Python. Using a general
+purpose programming language allows a Function to use more advanced logic to
+template resources, like loops and conditionals.
 
 {{<hint "important" >}}
-Composition functions are an alpha feature. Alpha features aren't enabled by
-default. 
+Composition functions are a beta feature. 
 {{< /hint >}}
 
-To attach a composition function to a Composition define a 
-{{<hover label="xfn" line="7">}}function{{</hover>}} inside the Composition
-{{<hover label="xfn" line="4">}}spec{{</hover>}}.
-
-Provide a {{<hover label="xfn" line="8">}}name{{</hover>}} for the function.   
-The {{<hover label="xfn" line="9">}}type{{</hover>}} is always `Container`.  
-The {{<hover label="xfn" line="11">}}container.image{{</hover>}} is the
-location of the composition function container image.
+To use composition functions define a {{<hover label="xfn"
+line="7">}}pipeline{{</hover>}} of steps inside the Composition {{<hover
+label="xfn" line="4">}}spec{{</hover>}}. Each {{<hover label="xfn"
+line="8">}}step{{</hover>}} calls a Function. You can't specify resource
+templates using the `resources` field when you specify a pipeline of Functions.
+You must set the Composition {{<hover label="xfn" line="6">}}mode{{</hover>}} to
+`Pipeline` to use Functions.
+
+Each {{<hover label="xfn" line="8">}}step{{</hover>}} must specify the {{<hover
+label="xfn" line="10">}}name{{</hover>}} of the Function to call. Some Functions
+also allow you to specify an {{<hover label="xfn" line="11">}}input{{</hover>}}.
+Different Functions each have a different {{<hover label="xfn"
+line="13">}}kind{{</hover>}} of input.
+
+This example uses Function Patch and Transform. Function Patch and Transform is
+a Function that implements Crossplane resource templates. You can use Function
+Patch and Transform to specify resource templates in a pipeline with other
+Functions.
 
 ```yaml {label="xfn",copy-lines="none"}
 apiVersion: apiextensions.crossplane.io/v1
 kind: Composition
 # Removed for Brevity
 spec:
-  resources:
   # Removed for Brevity
-  functions:
-  - name: rds-instance-password
-    type: Container
-    container:
-      image: xpkg.upbound.io/provider-aws-xfns/random-rds-password:v0.1.0
+  mode: Pipeline
+  pipeline:
+  - step: patch-and-transform
+    functionRef:
+      name: function-patch-and-transform
+    input:
+      apiVersion: pt.fn.crossplane.io/v1beta1
+      kind: Resources
+      resources:
+      - name: storage-bucket
+        base:
+          apiVersion: s3.aws.upbound.io/v1beta1
+          kind: Bucket
+          spec:
+            forProvider:
+              region: "us-east-2"
 ```
 
 Read the [composition functions]({{<ref "./composition-functions">}}) page for
@@ -1293,6 +1312,9 @@ Composition.
 When creating a Composition Crossplane automatically validates specific
 parameters in the Composition.
 
+If using `mode: Resources`:
+
+* The `resources` field isn't empty.
 * All resources either use a `name` or don't. Compositions can't use both named
   and unnamed resources.
 * No duplicate resource names.
@@ -1303,10 +1325,11 @@ parameters in the Composition.
 * Readiness checks using `matchString` aren't empty.
 * Readiness checks using `matchInteger` isn't `0`.
 * Readiness checks requiring a `fieldPath` value provide it.
-* If using composition functions, all resources must have names.
-* Composition function container field isn't empty.
-* Composition function `type` is `container`.
-* Composition function names are unique.
+
+If using `mode: Pipeline` (Composition Functions):
+
+* The `pipeline` field isn't empty.
+* No duplicate step names.
 
 ### Resource schema validation
 <!-- vale write-good.TooWordy = NO -->