[Prostgres Vector Store] Add PGVector Driver option + Fix null character issue w/ TypeORM Driver (#3367)

* Add PGVector Driver option + Fix null character issue w/ TypeORM Driver

* Handle file upload case with PGVector

* Cleanup

* Fix data filtering for chatflow uploaded files

* Add distanceStrategy parameter

* Fix query to improve chatflow uploaded files filtering

* Ensure PGVector release connections

* Await client connected

* Make Postgres credentials optionnal when set on env variables

* Document env variables in nodes directories

* Prevent reuse client

* Fix empty metadataFilter

* Update CONTRIBUTING.md

* Update Postgres.ts

---------

Co-authored-by: Henry Heng <henryheng@flowiseai.com>

packages/components/nodes/vectorstores/Postgres/driver/Base.ts

@@ -0,0 +1,48 @@
+import { VectorStore } from '@langchain/core/vectorstores'
+import { getCredentialData, getCredentialParam, ICommonObject, INodeData } from '../../../../src'
+import { Document } from '@langchain/core/documents'
+import { Embeddings } from '@langchain/core/embeddings'
+import { getDatabase, getHost, getPort, getTableName } from '../utils'
+
+export abstract class VectorStoreDriver {
+    constructor(protected nodeData: INodeData, protected options: ICommonObject) {}
+
+    abstract instanciate(metaDataFilters?: any): Promise<VectorStore>
+
+    abstract fromDocuments(documents: Document[]): Promise<VectorStore>
+
+    protected async adaptInstance(instance: VectorStore, _metaDataFilters?: any): Promise<VectorStore> {
+        return instance
+    }
+
+    getHost() {
+        return getHost(this.nodeData) as string
+    }
+
+    getPort() {
+        return getPort(this.nodeData) as number
+    }
+
+    getDatabase() {
+        return getDatabase(this.nodeData) as string
+    }
+
+    getTableName() {
+        return getTableName(this.nodeData)
+    }
+
+    getEmbeddings() {
+        return this.nodeData.inputs?.embeddings as Embeddings
+    }
+
+    async getCredentials() {
+        const credentialData = await getCredentialData(this.nodeData.credential ?? '', this.options)
+        const user = getCredentialParam('user', credentialData, this.nodeData, process.env.POSTGRES_VECTORSTORE_USER)
+        const password = getCredentialParam('password', credentialData, this.nodeData, process.env.POSTGRES_VECTORSTORE_PASSWORD)
+
+        return {
+            user,
+            password
+        }
+    }
+}