feat: APIM feature updates (#312)

APIM configuration can easily bloat your serverless configuration yaml. This PR reduces a lot of the boilerplate APIM configuration in many use cases except for when direct customization is required.

  Infers APIM operation configuration from HTTP binding
  Will automatically generate API just by setting apm: true in serverless yaml
  Will automatically generate default backend pointing to the /api endpoint of your function app
  Now supports configuring multiple API's in a single configuration
  Now supports configuring multiple Backends in a single configuration
  Ability to link an APIM operation to a specific API and backend

docs/examples/apim.md

@@ -2,11 +2,44 @@
 
 [API Management](https://azure.microsoft.com/en-us/services/api-management/) is an Azure Service for publishing, managing, securing and monitoring APIs. It can be deployed along with your Serverless function app by specifying its configuration in `serverless.yml`. Here is a basic example of how to configure API Mangement:
 
-## Simple Handler
+## Simple Configuration
+Simply setting `apim: true` in your configuration will automatically deploy a consumption based APIM resource to Azure.  By default it will create a API with path of `/api` in your APIM instance and will map all operations defined in the serverless yaml to your function app.
 
 ```yaml
 service: greeter
 
+provider:
+  prefix: greeter
+  name: azure
+  # Default to West US, allow for command line arg --region to override
+  region: ${opt:region, 'westus'}
+  # Default to dev, allow for command line arg -- stage to override
+  stage: ${opt:stage, 'dev'}
+  # Azure subscription ID for deployment
+  subscriptionId: 00000000-0000-0000-0000-000000000000
+
+  # Start of your API Management configuration
+  apim: true
+
+plugins:
+  - serverless-azure-functions
+
+functions:
+  hello:
+    handler: src/handlers/hello.handler
+    events:
+      - http: true
+        x-azure-settings:
+          methods:
+            - GET
+          authLevel : function
+```
+
+## Full Configuration
+In this example you can see the configuration support is quite verbose.  You have the ability to create multiple APIs and Backends as well as associate an operation to a specific api/backend.  If the operation is not specifically defined it will default to the first API / Backend that has been defined.
+```yaml
+service: greeter
+
 provider:
   prefix: greeter
   name: azure
@@ -20,25 +53,48 @@ provider:
   # Start of your API Management configuration
   apim:
     # API specifications
-    api:
-      # Name of the API
-      name: v1
-      subscriptionRequired: false
-      # Display name
-      displayName: v1
-      # Description of API
-      description: V1 sample app APIs
-      # HTTP protocols allowed
-      protocols:
-        - https
-      # Base path of API calls
-      path: v1
-      # Tags for ARM resource
-      tags:
-        - tag1
-        - tag2
-      # No authorization
-      authorization: none
+    apis:
+        # Name of the API
+      - name: products-api
+        subscriptionRequired: false
+        # Display name
+        displayName: Products API
+        # Description of API
+        description: The Products REST API
+        # HTTP protocols allowed
+        protocols:
+          - https
+        # Base path of API calls
+        path: products
+        # Tags for ARM resource
+        tags:
+          - tag1
+          - tag2
+        # No authorization
+        authorization: none
+        # Name of the API
+      - name: categories-api
+        subscriptionRequired: false
+        # Display name
+        displayName: Categories API
+        # Description of API
+        description: The Categories REST API
+        # HTTP protocols allowed
+        protocols:
+          - https
+        # Base path of API calls
+        path: categories
+        # Tags for ARM resource
+        tags:
+          - tag1
+          - tag2
+        # No authorization
+        authorization: none
+    backends:
+      - name: products-backend
+        url: api/products
+      - name: categories-backend
+        url: api/categories
     # CORS Settings for APIM
     cors:
       allowCredentials: false
@@ -59,26 +115,48 @@ plugins:
   - serverless-azure-functions
 
 functions:
-  hello:
-    handler: src/handlers/hello.handler
+  getProducts:
+    handler: src/handlers/getProducts.handler
 
     # API Management configuration for `hello` handler
     apim:
+      # The API to attach this operation
+      api: products-api
+      # The Backend use for the operation
+      backend: products-backend
       operations:
-        # GET operation for `hello` handler
+        # GET operation for `getProducts` handler
         - method: get
           # URL path for accessing handler
-          urlTemplate: /hello
+          urlTemplate: /
           # Display name inside Azure Portal
-          displayName: Hello
+          displayName: GetProducts
     events:
       - http: true
         x-azure-settings:
           methods:
             - GET
           authLevel : function
+  getCategories:
+    handler: src/handlers/getCategories.handler
+
+    # API Management configuration for `getCategories` handler
+    apim:
+      # The API to attach this operation
+      api: categories-api
+      # The Backend use for the operation
+      backend: categories-backend
+      operations:
+        # GET operation for `getCategories` handler
+        - method: get
+          # URL path for accessing handler
+          urlTemplate: /
+          # Display name inside Azure Portal
+          displayName: GetCategories
+    events:
       - http: true
         x-azure-settings:
-          direction: out
-          name: res
+          methods:
+            - GET
+          authLevel : function
 ```