chore: add (start share == end share) check in parse namespace (backp…

…ort #3709) (#3710)

## Overview

The start share shouldn't be equal to the end share because the range is
end-exclusive. This PR adds this check.
<hr>This is an automatic backport of pull request #3709 done by
[Mergify](https://mergify.com).

---------

Co-authored-by: sweexordious <[email protected]>

pkg/proof/proof_test.go

@@ -147,6 +147,13 @@ func TestNewShareInclusionProof(t *testing.T) {
 			namespaceID:   appns.TxNamespace,
 			expectErr:     true,
 		},
+		{
+			name:          "ending share is equal to the starting share",
+			startingShare: 1,
+			endingShare:   1,
+			namespaceID:   appns.TxNamespace,
+			expectErr:     true,
+		},
 		{
 			name:          "ending share higher than number of shares available in square size of 32",
 			startingShare: 0,

pkg/proof/querier.go

@@ -123,17 +123,14 @@ func QueryShareInclusionProof(_ sdk.Context, path []string, req abci.RequestQuer
 
 // ParseNamespace validates the share range, checks if it only contains one namespace and returns
 // that namespace ID.
+// The provided range, defined by startShare and endShare, is end-exclusive.
 func ParseNamespace(rawShares []shares.Share, startShare, endShare int) (appns.Namespace, error) {
 	if startShare < 0 {
 		return appns.Namespace{}, fmt.Errorf("start share %d should be positive", startShare)
 	}
 
-	if endShare < 0 {
-		return appns.Namespace{}, fmt.Errorf("end share %d should be positive", endShare)
-	}
-
-	if endShare < startShare {
-		return appns.Namespace{}, fmt.Errorf("end share %d cannot be lower than starting share %d", endShare, startShare)
+	if endShare <= startShare {
+		return appns.Namespace{}, fmt.Errorf("end share %d cannot be lower or equal to the starting share %d", endShare, startShare)
 	}
 
 	if endShare > len(rawShares) {