replace Content-Type with Accept on bodyless GET proxy routes

buildForwardHeaders now defaults to Accept: application/json instead of
Content-Type, since most callers are GET proxies with no body. POST/PUT
routes that send a body now set Content-Type explicitly.

closes #1002

Signed-off-by: Vishali <vsanghis@redhat.com>

Author: vishsanghishetty

components/frontend/src/app/api/auth/github/install/route.ts

@@ -7,7 +7,7 @@ export async function POST(request: Request) {
 
   const resp = await fetch(`${BACKEND_URL}/auth/github/install`, {
     method: 'POST',
-    headers,
+    headers: { ...headers, 'Content-Type': 'application/json' },
     body,
   })
 

components/frontend/src/app/api/auth/github/pat/route.ts

@@ -7,7 +7,7 @@ export async function POST(request: Request) {
 
   const resp = await fetch(`${BACKEND_URL}/auth/github/pat`, {
     method: 'POST',
-    headers,
+    headers: { ...headers, 'Content-Type': 'application/json' },
     body,
   })
 

components/frontend/src/app/api/auth/gitlab/connect/route.ts

@@ -7,7 +7,7 @@ export async function POST(request: Request) {
 
   const resp = await fetch(`${BACKEND_URL}/auth/gitlab/connect`, {
     method: 'POST',
-    headers,
+    headers: { ...headers, 'Content-Type': 'application/json' },
     body,
   })
 

components/frontend/src/app/api/auth/jira/connect/route.ts

@@ -7,7 +7,7 @@ export async function POST(request: Request) {
 
   const resp = await fetch(`${BACKEND_URL}/auth/jira/connect`, {
     method: 'POST',
-    headers,
+    headers: { ...headers, 'Content-Type': 'application/json' },
     body,
   })
 

components/frontend/src/app/api/cluster-info/route.ts

@@ -10,7 +10,7 @@ export async function GET() {
     const response = await fetch(`${BACKEND_URL}/cluster-info`, {
       method: 'GET',
       headers: {
-        'Content-Type': 'application/json',
+        'Accept': 'application/json',
       },
     });
 

components/frontend/src/app/api/feature-flags/route.ts

@@ -26,7 +26,7 @@ export async function GET(request: NextRequest) {
       method: 'GET',
       headers: {
         Authorization: clientKey,
-        'Content-Type': 'application/json',
+        'Accept': 'application/json',
       },
       next: { revalidate: 15 },
     });

components/frontend/src/app/api/projects/[name]/agentic-sessions/[sessionName]/git/configure-remote/route.ts

@@ -13,7 +13,7 @@ export async function POST(
     `${BACKEND_URL}/projects/${encodeURIComponent(name)}/agentic-sessions/${encodeURIComponent(sessionName)}/git/configure-remote`,
     {
       method: 'POST',
-      headers,
+      headers: { ...headers, 'Content-Type': 'application/json' },
       body,
     }
   );

components/frontend/src/app/api/projects/[name]/agentic-sessions/[sessionName]/repos/route.ts

@@ -13,7 +13,7 @@ export async function POST(
     `${BACKEND_URL}/projects/${encodeURIComponent(name)}/agentic-sessions/${encodeURIComponent(sessionName)}/repos`,
     {
       method: 'POST',
-      headers,
+      headers: { ...headers, 'Content-Type': 'application/json' },
       body,
     }
   );

components/frontend/src/app/api/projects/[name]/agentic-sessions/[sessionName]/workflow/route.ts

@@ -13,7 +13,7 @@ export async function POST(
     `${BACKEND_URL}/projects/${encodeURIComponent(name)}/agentic-sessions/${encodeURIComponent(sessionName)}/workflow`,
     {
       method: 'POST',
-      headers,
+      headers: { ...headers, 'Content-Type': 'application/json' },
       body,
     }
   );

components/frontend/src/app/api/projects/[name]/agentic-sessions/route.ts

@@ -33,7 +33,7 @@ export async function POST(
 
     const response = await fetch(`${BACKEND_URL}/projects/${encodeURIComponent(name)}/agentic-sessions`, {
       method: 'POST',
-      headers,
+      headers: { ...headers, 'Content-Type': 'application/json' },
       body,
     });