Mark google_sql_database.{charset,collation} as computed instead of h…

…aving defaults (hashicorp#229)

* Mark google_sql_database.{charset,collation} as computed instead of having defaults.

This change is required to avoid the following scenario:
When upgrading from a previous version of the Google provider, TF will change
the charset/collation of existing (TF-managed) databases to utf8/utf8_general_ci
(if the user hasn't added different config values before running TF apply),
potentially overriding any non-default settings that the user my have applied
through the Cloud SQL admin API. This violates POLA.

* Remove charset/collation defaults from the documentation, too.

* Add links to MySQL's and PostgreSQL's documentation about supported charset and collation values.

* Use version 5.7's docs instead of 5.6, since that's the most up to date version of MySQL that we support.

* Add a note that only UTF8 / en_US.UTF8 are currently supported for Cloud SQL PostgreSQL databases.

google/resource_sql_database.go

@@ -46,13 +46,13 @@ func resourceSqlDatabase() *schema.Resource {
 			"charset": &schema.Schema{
 				Type:     schema.TypeString,
 				Optional: true,
-				Default:  "utf8",
+				Computed: true,
 			},
 
 			"collation": &schema.Schema{
 				Type:     schema.TypeString,
 				Optional: true,
-				Default:  "utf8_general_ci",
+				Computed: true,
 			},
 		},
 	}

website/docs/r/sql_database.html.markdown

@@ -44,10 +44,23 @@ The following arguments are supported:
 * `project` - (Optional) The project in which the resource belongs. If it
     is not provided, the provider project is used.
 
-* `charset` - (Optional) The MySQL charset value (default "utf8").
-
-* `collation` - (Optional) The MySQL collation value (default
-    "utf8_general_ci").
+* `charset` - (Optional) The charset value. See MySQL's [Supported Character
+    Sets and
+    Collations](https://dev.mysql.com/doc/refman/5.7/en/charset-charsets.html)
+    and PostgreSQL's [Character Set
+    Support](https://www.postgresql.org/docs/9.6/static/multibyte.html)
+    for more details and supported values. Note that Cloud SQL's beta
+    offering for PostgreSQL databases currently only supports the charset value
+    `UTF8`.
+
+* `collation` - (Optional) The collation value. See MySQL's [Supported Character
+    Sets and
+    Collations](https://dev.mysql.com/doc/refman/5.7/en/charset-charsets.html)
+    and PostgreSQL's [Collation
+    Support](https://www.postgresql.org/docs/9.6/static/collation.html) for
+    more details and supported values. Note that Cloud SQL's beta
+    offering for PostgreSQL databases currently only supports the collation
+    value `en_US.UTF8`.
 
 ## Attributes Reference