Update go/xorm README with more detail on integrating EQL

languages/go/xorm/README.md

@@ -79,3 +79,168 @@ Run tests:
 ```shell
 ./run.sh tests
 ```
+
+## Integrating EQL into a Xorm app
+
+Before starting to integrate, follow the EQL installation steps in the main [README file](../../../README.md).
+
+The [goeql package](https://github.com/cipherstash/encrypt-query-language/blob/main/languages/go/goeql/goeql.go) contains functions to help with serializing data into the format that CipherStash Proxy expects and deserializing data from this format back to the original value.
+
+For reference there is an example setup in the [main.go](./main.go) file.
+
+Example migrations are in the [migrations.go](./migrations.go) file.
+
+Start with adding a new encrypted field:
+
+1. Add a custom type for the field.
+
+For example a text field:
+
+```go
+type EncryptedTextField string
+```
+
+jsonb field:
+
+```go
+type EncryptedJsonbField map[string]interface{}
+```
+
+2. Add the field/s to the relevant struct:
+
+```go
+type Example struct {
+	Id                  int64               `xorm:"pk autoincr"`
+	EncryptedTextField  EncryptedTextField  `json:"encrypted_text_field" xorm:"jsonb 'encrypted_text_field'"`
+	EncryptedJsonbField EncryptedJsonbField `json:"encrypted_jsonb_field" xorm:"jsonb 'encrypted_jsonb_field'"`
+}
+```
+
+3. Use the conversion interface to define a custom mapping rule for each field.
+
+Within each function use the goeql Serialize and Deserialize functions.
+
+When serializing the table name and column name need to be passed as arguments.
+
+Example for a text field:
+
+```go
+func (et EncryptedTextField) ToDB() ([]byte, error) {
+	etCs := goeql.EncryptedText(et)
+    // e.g table name is "examples" and field is "encrypted_text_field"
+	return (&etCs).Serialize("examples", "encrypted_text_field")
+}
+
+func (et *EncryptedTextField) FromDB(data []byte) error {
+	etCs := goeql.EncryptedText(*et)
+
+	val, err := (&etCs).Deserialize(data)
+	if err != nil {
+		return err
+	}
+
+	*et = EncryptedTextField(val)
+
+	return nil
+}
+```
+
+Example for a jsonb field:
+
+```go
+func (ej EncryptedJsonbField) ToDB() ([]byte, error) {
+	ejCs := goeql.EncryptedJsonb(ej)
+    // e.g table name is "examples" and field is "encrypted_jsonb_field"
+	return (&ejCs).Serialize("examples", "encrypted_jsonb_field")
+}
+
+func (ej *EncryptedJsonbField) FromDB(data []byte) error {
+	etCs := goeql.EncryptedJsonb(*ej)
+
+	val, err := (&etCs).Deserialize(data)
+	if err != nil {
+		return err
+	}
+
+	*ej = EncryptedJsonbField(val)
+
+	return nil
+}
+```
+
+4. Add a migration to add custom constraint checks for each field.
+
+These checks will validate that the json payload is correct and that encrypted data is being inserted correctly.
+
+Example:
+
+```sql
+	ALTER TABLE examples ADD CONSTRAINT encrypted_text_field_encrypted_check
+	CHECK ( cs_check_encrypted_v1(encrypted_text_field) );
+
+	ALTER TABLE examples ADD CONSTRAINT encrypted_jsonb_encrypted_check
+	CHECK ( cs_check_encrypted_v1(encrypted_jsonb_field) );
+```
+
+5. [Add indexes](../../../README.md#managing-indexes-with-eql):
+
+Example:
+
+```sql
+    SELECT cs_add_index_v1('examples', 'encrypted_text_field', 'unique', 'text', '{"token_filters": [{"kind": "downcase"}]}');
+    SELECT cs_add_index_v1('examples', 'encrypted_text_field', 'match', 'text');
+    SELECT cs_add_index_v1('examples', 'encrypted_text_field', 'ore', 'text');
+    SELECT cs_add_index_v1('examples', 'encrypted_jsonb_field', 'ste_vec', 'jsonb', '{"prefix": "some-prefix"}');
+
+    --   The below indexes will also need to be added to enable full search functionality on the encrypted columns
+
+    CREATE UNIQUE INDEX ON examples(cs_unique_v1(encrypted_text_field));
+    CREATE INDEX ON examples USING GIN (cs_match_v1(encrypted_text_field));
+    CREATE INDEX ON examples (cs_ore_64_8_v1(encrypted_text_field));
+    CREATE INDEX ON examples USING GIN (cs_ste_vec_v1(encrypted_jsonb_field));
+
+    --   Run these functions to activate
+
+    SELECT cs_encrypt_v1();
+    SELECT cs_activate_v1();
+```
+
+## Inserting
+
+Inserting data remains the same.
+
+The `toDB()` function that was setup in [this earlier step](README.md#integrating-eql-into-a-xorm-app), serializes the plaintext value into the json payload CipherStash Proxy expects.
+
+Retrieving data remains the same as well.
+
+The `fromDb()` function for the relevant encrypted field will deserialize the json payload returned from CipherStash Proxy and return the plaintext value
+
+## Querying
+
+The queries to retrieve data do change.
+
+EQL provides specialized functions to interact with encrypted data.
+
+You can read about these functions [here](../../../README.md#querying-data-with-eql).
+
+Similar to how CipherStash Proxy require's a specific json payload when inserting data, a similar payload is required when querying.
+
+Goeql has functions that will serialize a value into the format required by CipherStash Proxy.
+
+[These functions](https://github.com/cipherstash/encrypt-query-language/blob/main/languages/go/goeql/goeql.go#L153-L171) will need to be used for the relevant query.
+
+Examples of how to use these are in the [example_queries.go](./example_queries.go) file.
+
+Below is an example of running a match query on a text field.
+
+```go
+    query, errTwo := goeql.MatchQuery("some", "examples", "encrypted_text_field")
+	if errTwo != nil {
+		log.Fatalf("Error marshaling encrypted_text_field: %v", errTwo)
+	}
+
+	has, errThree := engine.Where("cs_match_v1(encrypted_text_field) @> cs_match_v1(?)", query).Get(&ExampleTwo)
+	if errThree != nil {
+		log.Fatalf("Could not retrieve exampleTwo: %v", errThree)
+	}
+```