fix: config to support keys with special values (#9304)

This PR adds context-based `k=v` splits based
on the sub-system which was obtained, if the
keys are not provided an error will be thrown
during parsing, if keys are provided with wrong
values an error will be thrown. Keys can now
have values which are of a much more complex
form such as `k="v=v"` or `k=" v = v"`
and other variations.

additionally, deprecate unnecessary postgres/mysql
configuration styles, support only

- connection_string for Postgres
- dsn_string for MySQL

All other parameters are removed.

cmd/config/config.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"io"
 	"regexp"
+	"sort"
 	"strings"
 
 	"github.com/minio/minio-go/v6/pkg/set"
@@ -196,6 +197,15 @@ func (kvs KVS) Empty() bool {
 	return len(kvs) == 0
 }
 
+// Keys returns the list of keys for the current KVS
+func (kvs KVS) Keys() []string {
+	var keys = make([]string, len(kvs))
+	for i := range kvs {
+		keys[i] = kvs[i].Key
+	}
+	return keys
+}
+
 func (kvs KVS) String() string {
 	var s strings.Builder
 	for _, kv := range kvs {
@@ -559,6 +569,33 @@ func (c Config) Clone() Config {
 	return cp
 }
 
+// Converts an input string of form "k1=v1 k2=v2" into fields
+// of ["k1=v1", "k2=v2"], the tokenization of each `k=v`
+// happens with the right number of input keys, if keys
+// input is empty returned value is empty slice as well.
+func kvFields(input string, keys []string) []string {
+	var valueIndexes []int
+	for _, key := range keys {
+		i := strings.Index(input, key+KvSeparator)
+		if i == -1 {
+			continue
+		}
+		valueIndexes = append(valueIndexes, i)
+	}
+
+	sort.Ints(valueIndexes)
+	var fields = make([]string, len(valueIndexes))
+	for i := range valueIndexes {
+		j := i + 1
+		if j < len(valueIndexes) {
+			fields[i] = strings.TrimSpace(input[valueIndexes[i]:valueIndexes[j]])
+		} else {
+			fields[i] = strings.TrimSpace(input[valueIndexes[i]:])
+		}
+	}
+	return fields
+}
+
 // SetKVS - set specific key values per sub-system.
 func (c Config) SetKVS(s string, defaultKVS map[string]KVS) error {
 	if len(s) == 0 {
@@ -581,9 +618,20 @@ func (c Config) SetKVS(s string, defaultKVS map[string]KVS) error {
 		return Errorf("sub-system '%s' only supports single target", subSystemValue[0])
 	}
 
+	tgt := Default
+	subSys := subSystemValue[0]
+	if len(subSystemValue) == 2 {
+		tgt = subSystemValue[1]
+	}
+
+	fields := kvFields(inputs[1], defaultKVS[subSys].Keys())
+	if len(fields) == 0 {
+		return Errorf("sub-system '%s' cannot have empty keys", subSys)
+	}
+
 	var kvs = KVS{}
 	var prevK string
-	for _, v := range strings.Fields(inputs[1]) {
+	for _, v := range fields {
 		kv := strings.SplitN(v, KvSeparator, 2)
 		if len(kv) == 0 {
 			continue
@@ -604,12 +652,6 @@ func (c Config) SetKVS(s string, defaultKVS map[string]KVS) error {
 		return Errorf("key '%s', cannot have empty value", kv[0])
 	}
 
-	tgt := Default
-	subSys := subSystemValue[0]
-	if len(subSystemValue) == 2 {
-		tgt = subSystemValue[1]
-	}
-
 	_, ok := kvs.Lookup(Enable)
 	// Check if state is required
 	_, enableRequired := defaultKVS[subSys].Lookup(Enable)