Fix parameter validation upon install/update (#554)

* Fix parameter validation upon install/update

**Why?**

When installing or updating ADF, it did not validate the input given by
the user. In some situations, this implied that it would attempt to
install/update failing minutes later. Or it might not work at all after
the CloudFormation deployment of the SAR template reports back as if
all went well.

One of the parameters, the deployment region was particularly dangerous
to leave blank on an update. As that would change the bucket name that
would be used by ADF to share resources.

**What?**

Added validations to the template.

The account alias regex was found here [0].
While the role name requirements were found at [1].

* [0](https://docs.aws.amazon.com/IAM/latest/APIReference/API_CreateAccountAlias.html)
* [1](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-iam-role.html#cfn-iam-role-rolename)

* Improve regex validation according to review

The Account Name requirements were fount at [0].

* [0](https://docs.aws.amazon.com/organizations/latest/APIReference/API_Account.html)

Author: sbkok

src/template.yml

@@ -30,48 +30,73 @@ Parameters:
   CrossAccountAccessRoleName:
     Type: String
     Default: OrganizationAccountAccessRole
+    AllowedPattern: "[a-zA-Z0-9_+=,.@\\-]+"
 
   MainNotificationEndpoint:
     Type: String
     Default: ""
-    Description: "Example -> jane@example.com"
+    Description: >-
+      Example -> jane@example.com. (Only required when installing ADF for the
+      first time.)
 
   DeploymentAccountName:
     Type: String
     Default: ""
-    Description: "The name of the new or existing deployment account"
+    AllowedPattern: "[\\s\\S]*"
+    MinLength: 0
+    MaxLength: 50
+    Description: >-
+      The name of the new or existing deployment account. (Only required when
+      installing ADF for the first time.)
 
   DeploymentAccountEmailAddress:
     Type: String
     Default: ""
-    Description: "The email address for the new or existing deployment account"
+    Description: >-
+      The email address for the new or existing deployment account. (Only required when
+      installing ADF for the first time.)
 
   DeploymentAccountAlias:
     Type: String
     Default: ""
-    Description: "(Optional) Example -> companyname-deployment (must be globally unique)"
+    AllowedPattern: "([a-z0-9](([a-z0-9]|-(?!-))*[a-z0-9])?)?"
+    MinLength: 0
+    MaxLength: 63
+    Description: >-
+      Example -> companyname-deployment (Must be globally unique. Only required when
+      installing ADF for the first time.)
 
   DeploymentAccountId:
     Type: String
+    AllowedPattern: "(\\d{12})?"
     Default: ""
     Description: >-
-      Example -> 123456789012  (Only required if you have an existing AWS Account
-      that you wish to use as the deployment account.)
+      Example -> 123456789012  (Only supported when installing ADF for the first time
+      and you have an existing AWS Account that you wish to use as the deployment
+      account. Leave blank otherwise.)
 
   DeploymentAccountMainRegion:
     Type: String
-    Default: ""
+    AllowedPattern: "(us(-gov)?|ap|ca|eu|sa)-(central|(north|south)?(east|west)?)-\\d"
+    MinLength: 6
     Description: "Example -> us-east-1, us-gov-west-1, eu-west-1"
 
   DeploymentAccountTargetRegions:
     Type: CommaDelimitedList
     Default: ""
-    Description: "(Optional) Example -> us-east-1, us-west-1, eu-west-3"
+    Description: >-
+      (Optional) Example -> us-east-1, us-west-1, eu-west-3. (Only supported when
+      installing ADF for the first time. If you would like to update this later,
+      please look at the adfconfig.yml file in the aws-deployment-framework-bootstrap
+      repository.)
 
   ProtectedOUs:
-    Description: "(Optional) Example -> ou-123,ou-234"
     Type: CommaDelimitedList
     Default: ""
+    Description: >-
+      (Optional) Example -> ou-123,ou-234 (Only supported when installing ADF for
+      the first time. If you would like to update this later, please look at the
+      adfconfig.yml file in the aws-deployment-framework-bootstrap repository.)
 
   LogLevel:
     Description: >-