docs(spanner): clarify how to set paramters

- include param in DSN example
- link to README docs on param (option) format
- switch to 'parameter' instead of 'option', in the main README, since
this is preferred

README.md

@@ -41,7 +41,7 @@ Database drivers run migrations. [Add a new database?](database/driver.go)
 
 ### Database URLs
 
-Database connection strings are specified via URLs. The URL format is driver dependent but generally has the form: `dbdriver://username:password@host:port/dbname?option1=true&option2=false`
+Database connection strings are specified via URLs. The URL format is driver dependent but generally has the form: `dbdriver://username:password@host:port/dbname?param1=true&param2=false`
 
 Any [reserved URL characters](https://en.wikipedia.org/wiki/Percent-encoding#Percent-encoding_reserved_characters) need to be escaped. Note, the `%` character also [needs to be escaped](https://en.wikipedia.org/wiki/Percent-encoding#Percent-encoding_the_percent_character)
 

database/spanner/README.md

@@ -2,12 +2,14 @@
 
 ## Usage
 
+See [Google Spanner Documentation](https://cloud.google.com/spanner/docs) for
+more details.
+
 The DSN must be given in the following format.
 
-`spanner://projects/{projectId}/instances/{instanceId}/databases/{databaseName}`
-
-See [Google Spanner Documentation](https://cloud.google.com/spanner/docs) for details.
+`spanner://projects/{projectId}/instances/{instanceId}/databases/{databaseName}?param=true`
 
+as described in [README.md#database-urls](../../README.md#database-urls)
 
 | Param | WithInstance Config | Description |
 | ----- | ------------------- | ----------- |
@@ -18,7 +20,6 @@ See [Google Spanner Documentation](https://cloud.google.com/spanner/docs) for de
 | `instanceId` || The id of the instance running Spanner
 | `databaseName` || The name of the Spanner database
 
-
 > **Note:** Google Cloud Spanner migrations can take a considerable amount of 
 > time. The migrations provided as part of the example take about 6 minutes to 
 > run on a small instance.
@@ -42,4 +43,4 @@ In order to be able to use more than 1 DDL statement in the same migration file,
 
 To unit test the `spanner` driver, `SPANNER_DATABASE` needs to be set. You'll
 need to sign-up to Google Cloud Platform (GCP) and have a running Spanner
-instance since it is not possible to run Google Spanner outside GCP.
+instance since it is not possible to run Google Spanner outside GCP.